OPTOMETRY  LIBRARY 


RETINOSCOPY 

(SHADOW  TEST) 


THORINGTON 


Reviews  of  Previous  Editions  of 

Thorington's   Retinoscopy. 


From  "The. Medical  Record,"  New  York. 

"This  little  manual  deserves  a  second  edition,  and  will  undoubtedly  pass  througli 
many  more.  It  presents  a  clear,  terse,  and  thorough  exposition  of  an  objective 
method  of  determining  refraction  errors  which  is  deservedly  increasing  in  popularity. 
In  our  opinion  the  author  is  amply  justified  in  declaring  that  its  great  value  in 
nystagmus,  young  children,  amblyopia,  aphakia,  and  in  examining  illiterates  and 
the  feeble-minded  cannot  be  overestimated,  and  we  agree  with  him  in  reminding 
those  who  attempt  retinoscooy,  fail,  and  ridicule  it,  that  the  fault  is  behind  and 
not  in  front  of  the  mirror.     The  book  is  well  printed  and  usefully  illustrated." 

From  "The  Annals  of  Ophthalmology,"  St.  Louis,  Mo. 

Retinoscopy  has  come  to  stay.  It  is  not  a  fad,  neither  a  fashion.  It  is  scien- 
tific, and  withal  &o  eminently  practical  in  its  application  as  to  commend  it  to  every 
thinking  worker  in  ophthalmology.  The  tendency  in  the  medicine  of  to-day  is  to- 
ward objective  methods.  An  objective  method  must  possess  two  attributes: 
exactness  and  absolute  independence  of  the  patient's  testimony.  In  addition  to 
these  qualities,  an  objective  method  must,  if  it  is  to  meet  with  general  acceptance, 
be  easy  of  application.  Ophthalmoscopy  and  ophthalmometry  are  but  relatively 
exact  in  refractive  work,  seeing  which  the  trial-case  has  held  its  supremacy  up  to 
date;  nor  would  we  wish  to  relegate  it  to  the  background.  With  a  patient  whose 
testimony  is  trustworthy  exact  results  are  thus  obtainable,  but  it  requires  the 
most  intelligent  cooperation  on  the  part  of  the  examined.  If,  however,  there  be 
but  the  least  departure  from  the  conditions  essential  to  close  work  with  the  test- 
lenses — as,  for  instance,  with  foreigners,  illiterates,  children,  partial  amblyopics, 
or  mental  astigmatics — retinoscooy  stands  ready  to  furnish  a  verdict  from  which 
there  can  be  no  appeal,  when  one  has  learned  to  properly  inter^^ret  the  movements 
observed  in  the  pupillary  area.  It  is  to  the  elucidation  of  these  latter  movements 
as  observed  through  a  plane  mirror  at  a  distance  of  one  meter  that  Dr.  Thorington 
devotes  himself  in  the  volume  before  us.  The  treatment  of  the  subject  is  so  beauti- 
fully simple  that  one  who  runs  may  read." 

From  "The  Journal  of  the  American  Medical  Association,"  Chicago,  111. 

"The  author  of  this  well-written  little  book  has  very  satisfactorily  described 
the  most  approved  methods  of  retinoscopy.  The  work  is  especially  valuable  in 
that  for  a  great  part  it  details  the  results  of  personal  investigation  of  so  well-known 
an  authority  on  this  subject  as  Dr.  Thorington.  Oculists  accustomed  to  casually 
use  retinoscopy  as  practised  in  the  old  way,  with  the  concave  mirror  or  with  the 
ophthalmoscopic  mirror,  will  be  surprised  to  note  the  marked  evolution  of  the 
modus  operandi  of  this  test  as  developed  by  Drs.  Jackson  and  Thorington.  With 
perfected  instruments  and  strict  attention  to  arrangement  of  light,  distance,  and 
other  details,  a  surprising  degree  of  proficiency  and  accuracy  is  possible.  Any 
one  pursuing  the  modern  methods  of  retinoscopy  will  soon  be  convinced  of  its 
superiority  over  all  other  objective  tests,  and  every  worker  in  ophthalmology 
realizes  the  necessity  of  at  least  one  reliable  objective  method  of  refraction." 

From  "The  New  Orleans  Medical  and  Surgical  Journal,"  New  Orleans,  La. 

"  We  have  nothing  but  a  good  word  for  this  little  book.  It  seems  to  fulfil  well 
the  purpose  intended.  It  gives  a  brief,  clear  description  of  the  means  and  manner 
of  retinoscopy,  together  with  the  principles  or  natural  laws  upon  which  it  is  founded. 
The  author  has  done  well  in  selecting  the  method  he  thinks  best  and  simplest, 
and  has  confined  himself  to  it,  so  that  the  student  will  have  no  difficulty  or  con- 
fusion in  following  the  manual  step  by  step,  and  learning  to  put  in  practice  for  him- 
self what  is  described  in  the  pages.  This  once  accomplished,  he  can  readily,  if 
he  becomes  convinced  of  its  usefulness,  acquire  the  variations  and  refinements 
upon  this  mode  of  examination." 

From  "The  New  York  Medical  Journal,"  New  York. 

"This  little  book  presents  as  simple  and  practical  a  description  of  the  shadow 
test  as  exists  in  our  language. 


From  "The  Scottish  Medical  and  Surgical  Journal,"  Edinburgh,  Scotland. 

"Dr.  Thorington's  lucid  text  is  accompanied  by  twenty-four  good  illustrations, 
and  on  every  page  one  notes  that  careful  attention  has  been  paid  to  little  details  of 
manipulation  which  stamp  the  writer  as  a  practical  teacher." 

From  "The  Homeopathic  Eye,  Ear,  and  Throat  Journal,"  New  York. 

"A  practical  and  useful  book.  This  is  one  of  the  most  concise  and  clearest 
explanations  of  this  subject  we  have  seen,  Retinoscopy  is  one  of  the  most  valu- 
able aids  we  have  in  refractive  work." 

From  "The  Denver  Medical  Times,"  Denver,  Col. 

"His  directions  and  descriptions  are  exceptionally  clear  and  concise,  and  the 
little  book  he  has  written,  we  think,  will  be  helpful  to  every  physician  who  is  in- 
terested in  the  fitting  of  glasses." 

From  "The  Chicago  Medical  Record,"  Chicago,  111. 

"This  little  book  is  the  most  practial  and  complete  exposition  of  the  value  and 
application  of  the  shadow  test  in  determining  refractive  errors  with  which  we 
have  any  acquaintance.  The  illustrations,  directions,  advice,  and  general  inform- 
ation in  the  book  are  all  admirable  " 

From  „The  Post-Graduate,"  New  York. 

"  This  work  on  retinoscopy  is  divided  into  six  chapters  and  an  index.  As  stated 
in  the  preface,  it  is  an  abstract  of  the  author's  previous  writings  and  lectures  on 
retinoscopy,  delivered  at  the  Philadelphia  Polyclinic.  It  is  intended  for  college 
students  and  post-graduates,  yet  it  is  sufficiently  complete  for  the  use  of  the  oph- 
thalmologist. Retinoscooy  has  been  selected  as  the  name  of  the  test,  as  it  is  the 
retina  in  its  relative  position  to  the  refractive  media  which  is  studied.  Skiascopy 
and  skiagraphy  are  therefore  regarded  as  misleading.  To  all  those  who  are  inter- 
ested in  this  test  for  the  determining  of  refraction  we  commend  the  work." 

From  "The  Philadelphia  Polyclinic,"  Philadelphia. 

"We  take  pleasure  in  commending  this  concise  statement  of  the  methods  to 
be  employed  in  the  routine  use  of  a  most  valuable  objective  means  of  determining 
the  errors  of  refraction.  The  student  is  told  in  simple  English  how  to  proceed  in 
the  examination." 

From  „The  Boston  Medical  and  Surgical  Journal,"  Boston,  Mass. 

"This  little  manual  is  certainly  the  clearest  exposition  of  this  method  of  esti- 
mating refraction  of  the  eye  that  has  yet  been  published.  The  methods  described 
are  not  so  complicated  as  those  taught  in  some  other  handbooks.  The  text  is  clear, 
and  the  illustrations  serve  the  purpose  for  which  they  were  designed  admirably. 
Taken  altogether,  it  is  the  most  practicable  handbook  on  retinoscopy  yet  pub- 
lished." 

From  "The  Journal  of  Ophthalmology,  Otology,  and  Laryngology,"  New  York. 

"  We  most  emphatically  recommend  this  little  book  to  the  beginner  in  the  study 
of  this  method  of  determining  refraction.  The  title  is  an  index  of  the  character 
of  the  text.  It  is  positive,  exact,  practical.  The  aim  of  the  author  has  been  to 
present  facts,  and  in  as  small  space  as  possible.  He  has  succeeded  absolutely. 
The  average  work  on  this  subject  is,  to  the  beginner,  somewhat  confusing,  from 
the  amount  of  theory  presented — theory  which  is  not  always  clear  to  the  student. 
This  has  been  avoided  in  the  present  case.  Little,  if  any,  theory  is  included,  and 
the  monograph  is  a  series  of  categorical  statements — clear,  precise,  and  sufficient." 


***The  price  of  this  book  (sixth  edition,  revised  and  enlarged, 
with  seven  additional  illustrations)  is  $1.00  net,  upon  receipt  of 
which  it  will  be  sent  postpaid  to  any  address.  It  may  be  obtained 
from  the  publishers  or  through  any  bookseller  or  dealer  in  opti- 
cians' supplies. 


BY  THE  SAME  AUTHOR 


Refraction  and  How  to  Refract.  With  251 
Illustrations,  many  of  which  are  from  Original  Draw- 
ings, Thirteen  being  Colored.  Fifth  Edition. 
Cloth,  net  $1.50. 

"It  is  a  sterling  book." — Annals  of  Ophthalmology. 

"There  is  not  a  word  of  trash  from  cover  to  cover;  everything 
is  concise,  accurate,  suflQcient,  and  up  to  date." — The 
Journal  of  Ophthalmology,  Otology  and  Laryngology. 

"It  is  clearly  written  and  very  fully  illustrated,  and  will  furnish 
an  aid  to  the  understanding  of  much  that  is  often  prac- 
tically Greek  to  others  than  specialists." — Journal  of  the 
American  Medical  Association,  Chicago. 

"It  will  be  found  extremely  useful  to  students,  and  will  also 
be  of  great  use  to  practitioners  who  want  a  handy  book  of 
reference,  and  one  which  is  not  overcrowded  with  minute 
details  which  are  of  theoretical  interest  only." — British 
Medical  Journal,  London. 

The  Ophthalmoscope  and  How  to  Use  It.  With 
Description  and  Treatment  of  the  Principal  Diseases 
of  the  Fundus.  12  Colored  Plates  and  73  other 
Illustrations.     Cloth,  net  $2.50. 

"Dr.  Thorington  has  presented  the  principles  involved  in  the 
clearest  possible  fashion,  and  his  directions  for  the  learner 
are  admirably  conceived  and  expressed." — Med.  Record. 

"A  lucid  exposition  of  practical  ophthalmoscopy.  The  book 
is  written  for  the  student  and  general  practitioner,  and 
really  fills  a  needed  want,  for  other  works  on  this  subject 
are  too  elaborate  or  too  compact  for  their  purposes." — 
Ophthalmology . 

P.  Blakiston's  Son  &  Co.,  Publishers,  Philadelphia 


RETINOSCOPY 


(OR  SHADOW  TEST) 


IN  THE 


DETERMINATION  OF  REFRACTION  AT  ONE  METER 
DISTANCE,  WITH  THE  PLANE  MIRROR 


BY 

JAMES  THORINGTON,  A.  M.,  M.  D. 

AUTHOR    OF    "refraction    AND    HOW    TO    REFACT     ;        THE    OPHTHALMOSCOPE    AND 

HOW  TO  USE  IT**;  PROFESSOR  OF  DISEASES  OP  THE  EYE  IN  THE  PHILADELPHIA 

POLYCLINIC  AND  COLLEGE  FOR  GRADUATES  IN  MEDICINE;  OPHTHALMIC 

SURGEON  TO   THE  PRESBYTERIAN   HOSPITAL;   OPHTHALMOLOGIST 

TO  THE  ELWYN  AND  VINELAND  TRAINING  SCHOOLS  FOR 

FEEBLE-MINDED    CHILDREN. 


SIXTH  EDITION,  REVISED  AND  ENLARGED 


SIXTY-ONE  ILLUSTRATIONS 

TEN  OF  WHICH  ARE  COLORED 


PHILADELPHIA 

P.    BLAKISTON'S   SON   &   CO 

1012   WALNUT  STREET 
1912 


°^^f 


Copyright,  1911,  by  James  Thorington,  M.  D. 


Printed   by 

The  Maple  Press 

York,  Pa, 


THIS    BOOK   IS    AFFECTIONATELY    DEDICATED   TO    THE 
MEMORY    OF 

FELIX  A.  BETTELHEIM,  Ph.D.,  M.D., 

MY    FRIEND   AND   ASSOCIATE    DURING  HIS    SIX   YEARS'     RESI- 
DENCE   AS    SURGEON    OF   THE    PANAMA   RAILROAD 
COMPANY,   AT   PANAMA. 


238190 


PREFACE  TO  THE  SIXTH  EDITION 


The  proof  of  the  growing  popularity  of  Retinoscopy  as 
the  most  valuable  objective  method  of  estimating  the 
refraction  of  an  eye  is  attested  by  the  demand  for  another 
edition. 

The  writer  takes  pleasure  in  carefully  revising  the  work 
and  bringing  it  up  to  date  by  the  addition  of  new  illustrations 
as  well  as  illustrations  of  new  apparatus. 

The  author  wishes  to  express  his  deep  appreciation  for 

the  many  favorable  criticisms  of  the  work  and  trusts  that 

this  edition  may  receive  continued  favor. 

2031  Chestnut  Street, 
Philadelphia,  Pa. 


IX 


PREFACE  TO  THE  FIRST  EDITION. 


At  the  earnest  solicitation  of  many  students  and  friends, 
this  book  is  presented  as  an  abstract  of  the  author's  previous 
writings  and  lectures  on  Retinoscopy,  delivered  during  the 
winter  course  on  Ophthalmology,  at  the  Philadelphia 
Polyclinic. 

In  presenting  a  manual  of  this  kind  the  writer  does  not 
presume  to  detract  from  the  writings  or  teachings  of  others, 
or  the  excellent  work  on  Skiascopy,  by  his  friend  and  col- 
league, Dr.  E.  Jackson;  but  wishes  to  elucidate  in  as  con- 
cise a  manner  and  few  words  as  possible  the  method  of 
applying  retinoscopy,  which  has  given  most  satisfaction  at 
his  hands. 

While  intended  for  college  students  and  post-graduates, 
yet  there  is  ample  material  given  w^hereby  the  ophthalmol- 
ogist at  a  distance  may  acquire  a  working  knowledge  of 
the  method,  by  study  and  practice  in  his  office. 

For  three  reasons  Retinoscopy,  in  preference  to  Skias- 
copy, has  been  chosen  as  the  title : 

First,  that  it  may  not  be  confounded  with  Skiagraphy. 

Second,  that  it  is  the  name  by  which  the  test  is  univer- 
sally known;  and — 

Third,  that  it  is  the  retina  in  its  relative  position  to  the 

dioptric  media  which  we  study. 
2031  Chestnut  Street, 
Philadelphia,  Pa. 


XI 


CONTENTS. 


CHAPTER  I. 

PAGE 

Definition. — Names. — Principle  and  Value  of  Retinoscopy. — 
Suggestions  to  the  Beginister, i 

CHAPTER  II. 

Retinoscope. — Light. — Light-screen. — ^Bracket. — Dark  Room. — 
Source  of  Light  and  Position  of  Mirror. — Observer  and 
Patient. — Luminous  Retinoscope, 6 

CHAPTER  HI. 

Distance  of  Surgeon  from  Patient. — Arrangement  of  Patient. 
Light,  and  Observer. — Reflection  from  Mirror. — How  to  Use 
the  Mirror. — What  the  Observer  Sees. — Retinal  Illumina- 
tion.— Shadow. — Where  to  Look  and  What  to  Look  For,  ...   17 

CHAPTER  IV. 

Point  of  Reversal. — To  Find  the  Point  of  Reversal. — What  to 
Avoid. — Direction  of  Movement  of  Retinal  Illumination.— 
Rate  of  Movement  and  Form  of  Illumination. — Rules  for 
Lenses. — Movement  of  Mirror  and  Apparatus, 27 

CHAPTER  V. 

Retinoscopy  in  Emmetropia  and  the  Various  Forms  of  Regular 
Ametropia. — Axonometer, 37 

CHAPTER  VI. 

Retinoscopy  in  the  Various  Forms  of  Irregular  Ametropia. — 
Retinoscopy  without  a  Cycloplegic. — The  Concave  Mirror. 
— Description  of  the  Author's  Schematic  Eye  and  Light- 
screen. — Lenses  for  the  Study  of  the  Scissor  Mox^ement, 
Conic  Cornea,  and  Spheric  Aberration, 54 

INDEX,      69 


Xlll 


LIST  OF  ILLUSTRATIONS. 


Figure  Page 

1.  Schematic  Eye  for  Studying  Retinoscopy 3 

2.  Retinoscope      7 

3.  Latest  Model  Retinoscope 7 

4.  Lettered  Retinoscope      8 

5.  Extension  Bracket 9 

6.  Oil  Lamp 10 

7.  Light-screen,  or  Cover  Chimney 12 

8.  New  Light-screen ,12 

9.  Electric  Retinoscope 13 

10,  Electric  Retinoscope 13 

11.  The  De  Zeng  Ideal  Electric  Retinoscope. 15 

12    Showing   Distance  from  Patient's   Eyes,  and  Equivalent  in 

Diopters 18 

13.  Arrangement  of  Patient,  Light  and  Oculist 19 

14.  Light    above   Patient's   Head    and    Oculist    at    One   Meter 

Distance 20 

15.  Mirror  Held  Correctly  before  Right  Eye 21 

16.  Correct  Position  for  Mirror 22 

17  and  18.  Mirror  with  Folding  Handle     ...........   23 

19.  Illumination  in  an  Emmetropic  Eye 24 

20.  Illumination  and  Shadow 24 

21.  Illumination  with  Straight  Edge 32 

22.  Illumination  with  Crescent  Edge      32 

2^.  Wiirdemann's  Disc 33 

24.  Jeiming's  Skiascopic  Disc      34 

25.  Trial-frame 35 

26.  Trial-case 36 

27.  Gray  Reflex  as  seen  in  High  Hyperopia      37 

28.  Gray  Reflex,  with  Crescent  Edge 37 

29.  Hyperopia 38 

30.  Refracted  Hyperopia 39 

31.  Emmetropia 40 

XV 


XVI  LIST    OF    ILLUSTRATIONS. 

Figure  Page 

32.  Refraction  of  Macula  Reigon 41 

:iS'  Myopia 42 

34.  Refracted  Myopia 43 

35.  Method  of  Writing  a  Formula 45 

36.  Band  of  Light      46 

37.  Band  of  Light  with  Straight  Edge 46 

38.  Band  of  Light  Astigmatism  Axis  90°       47 

39.  Band  of  Light  Showing  Half  a  Diopter  of  Astigmatism   ...  48 

40.  Axonometer      49 

41.  Axonometer  in  Position 50 

42.  Late  Model  Axonometer 50 

43.  Axonometer  in  Position  Indicating  Symmetric  Astigmatism    .  51 

44.  Axonometers  in  Position  Indicating  Asymmetric  Astigmatism  .  52 
45  and  46.  Irregular  Lentigular  Astigmatism 55 

47.  Scissor  Movement 56 

48.  Light  Area,  with  Dark  Interspace 57 

49.  Light  Areas  Brought  Together 57 

50.  Tilting  of  Lens 58 

51.  Scissor  Movement  after  Cataract      59 

52.  Illumination  Seen  in  Conic  Cornea    . 60 

53.  Positive  Aberration 61 

54.  Negative  Aberration 62 

55.  Lens  for  the  Study  of  the  Scissor  Movement      66 

56.  Lens  for  Study  of  the  Scissor  Movement 67 

57.  Lens  for  the  Study  of  Conic  Cornea 66 

58.  Lens  for  Study  of  Conic  Cornea 67 

59.  Lens  for  the  Study  of  Spheric  Aberration 66 

60.  Lens  for  Study  of  Spheric  Aberration 68 

61.  Lens  for  Study  of  Irregular  Lenticular  Astigmatism    ....  68 


RETINOSCOPY. 


CHAPTER  I. 


DEFINITION.— NAMES.— PRINCIPLE  AND  VALUE  OF  RET- 
INOSCOPY.—SUGGESTIONS  TO   THE  BEGINNER. 

Definition. — Retinoscopy  (see  preface  to  the  first  edition) 
may  be  defined  as  the  method  of  estimating  the  refraction 
of  an  eye  by  reflecting  into  it  rays  of  light  from  a  plane  or 
concave  mirror,  and  observing  the  movement  which  the 
retinal  illumination  makes  when  tilting  the  mirror  and 
reflecting  the  light  through  the  different  meridians. 

Names. — Shadow  test,  dioptroscopy,  fundus-reflex  test, 
keratoscopy,  fantoscopy,  pupilloscopy,  retinophotoscopy, 
retinoskiascopy,  skiascopy,  umbrascopy,  koroscopy,  etc., 
are  some  of  the  other  names  given  to  this  method  of  esti- 
mating the  refraction,  and  their  number  and  greater  or 
less  inappropriateness  have  had  much  to  do,  no  doubt, 
with  keeping  retinoscopy  in  the  background  of  ophthal- 
mology instead  of  giving  it  the  prominence  which  it  more 
justly  deserved  and  is  now  receiving  from  ophthalmologists 
in  all  parts  of  the  world. 

The  principle  of  retinoscopy  is  the  finding  of  the  point 
of  reversal  (the  far-point  of  a  myopic  eye),  and  to  do  this, 
if  an  eye  is  not  already  sufficiently  myopic,  it  will  be  neces- 
sary to  place  in  front  of  it  such  a  lens,  or  series  of  lenses,  as 
will  bring  the  emergent  rays  of  light  to  a  focus  at  a  certain 
definite  distance,  usually  at  one  meter  (see  Point  of  Reversal, 
Chap.  IV). 


Value  of  Retinoscopy. — Those  who  would  criticize 
retinoscopy  because  "we  see  nothing  and  think  nothing 
of  the  condition  of  the  fundus,"  base  their  criticism  appar- 
ently on  the  name  retinoscopy,  rather  than  from  any  great 
amount  of  practical  experience  with  the  method.  While 
admitting  that  the  ophthalmoscope  in  front  of  a  well-trained 
eye  will  often  give  a  close  estimate  of  the  refractive  error  of 
the  eye  under  examination,  yet  only  to  the  few  does  such 
skill  obtain,  and  even  then  there  is  that  uncertainty  which 
does  not  attach  itself  to  the  retinoscope  in  competent  hands. 
The  ophthalmologist  who  knows  how  to  use  the  retinoscopic 
mirror  accurately  has  the  advantage  of  his  confreres  who 
are  ignorant  of  the  test;  it  gives  him  a  position  decidedly 
independent  of  his  patient,  and  puts  him  above  the  common 
level  of  those  who  are  tied  to  the  trial-lenses  and  the  patient's 
uncertain  answers.  Furthermore,  when  it  is  remembered 
that  from  fifty  to  eighty  per  cent,  of  the  patients  consulting 
the  ophthalmologist  do  so  for  an  error  of  refraction,  it  is 
well  that  he  be  most  capable  in  this  important  branch  of 
the  subject. 

The  wonderful  advantage  of  retinoscopy  over  other 
methods  needs  no  argument  to  uphold  it;  the  rapidly  in- 
creasing number  of  retinoscopists  testify  to  its  merits. 

The  writer,  from  his  constant  use  of  the  mirror,  would 
suggest  the  following  axiom:  That,  with  an  eye  otherwise 
normal  except  for  its  refractive  error j  and  being  under  the 
influence  of  a  reliable  cycloplegic,  there  is  no  more  accurate 
objective  method  of  obtaining  its  exact  correction  than  by 
retinoscopy. 
Y~^etinoscopy  gives  the  following  advantages : 

The  character  of  the  refraction  is  quickly  diagnosed. 

The  exact  refraction  is  obtained  without  questioning 
the  patient. 

Littk  time  is  required  to  make  the  test. 


VALUE   OF   RETINOSCOPY. 


No  expensive  apparatus  is  necessarily  required. 

Its  great  value  can  never  be  overestimated  in  cases  of 
nystagmus,  young  children,  amblyopia,  aphakia,  illiterates, 
and  the  feeble-minded. 

From  what  has  just  been  written,  it  must  not  be  under- 


FiG.  I. — The  Author's  Schematic  Eye  For  Studying  Retinoscopy. 
{For  description,  see  Chapt.  VI.) 

stood  that  the  patient's  glasses  are  ordered  immediately 
from  the  findings  obtained  by  retinoscopy;  for,  on  the 
contrary,  all  retinoscopic  work,  like  ophthalmometry 
in  general,  should,  when  possible,  ■  be  confirmed  at  the 
trial-case. 

It  is  only  in  the  feeble-minded,  in  young  children,  and 


4  RETINOSCOPY. 

in  cases  of  amblyopia  that  glasses  are  ordered  direct  from 
the  findings  obtained  in  the  dark  room. 

The  subjective  method  of  placing  lenses  before  the 
patient's  eyes  and  letting  him  decide  by  asking  "is  this 
better?"  or  "is  this  worse?"  only  too  often  fatigues  the 
examiner  and  worries  the  patient,  giving  him  or  her  a  dread 
or  fear  of  inaccuracy  that  does  not  satisfy  the  surgeon  or 
tend  to  inspire  the  patient.  Whereas,  when  the  neutral- 
izing lenses  found  by  retinoscopy  are  placed  before  the 
patient's  eyes  and  he  obtains  a  visual  acuity  of  I  or  ||-  or 
more,  it  is  easy,  if  there  is  any  doubt,  to  hold  up  a  plus  and 
a  minus  quarter  diopter  glass  respectively  in  front  of  this 
correction,  and  let  the  patient  tell  at  once  if  either  glass 
improves  or  diminishes  the  vision. 

The  writer  is  not  condemning  the  subjective  or  other 
methods  of  estimating  the  refraction,  nor  is  he  trying  to 
extol  too  highly  the  shadow  test,  yet  he  would  remind  those 
who  try  retinoscopy,  fail,  and  then  ridicule  it,  that  the 
fault  with  them  is  hack  and  not  in  front  of  the  mirror. 

Suggestions  to  the  Beginner. — To  obtain  proficiency 
in  retinoscopy  there  is  much  to  be  understood.  Careful 
attention  to  details  must  be  given,  and  not  a  little  patience 
possessed,  as  it  is  not  a  method  that  is  acquired  in  a  day, 
and  it  is  only  after  weeks  of  constant  application  that 
accuracy  is  acquired.  Therefore  the  beginner  is  strongly 
advised  to  learn  the  major  points  from  one  of  the  many 
schematic  eyes  in  the  market  before  attempting  the  human 
eye.  At  the  same  time  he  should  be  perfectly  familiar 
with  the  action  of  the  d'fferent  cycloplegics  and  the  laws  of 
refraction  and  dioptrics,  as  an  understanding  of  conjugate 
foci  is  really  the  underlying  principle  of  the  method — i.e,, 
a  point  on  the  retina  being  one  focus  and  the  myopic  or 
artificially-made  far-point  the  other  focus. 

What  is  meant  by  major  points  applies  more  particularly 


SUGGESTIONS    TO   THE    BEGINNER.  5 

to  the  study  of  the  retinal  illumination,  its  direction  and 
apparent  rate  of  movement  when  the  mirror  is  tilted,  also 
the  form  or  shape  of  the  illumination,  the  distance  between 
the  observer  and  the  patient,  how  to  handle  the  mirror, 
etc.,  all  of  which  are  referred  to  under  their  special  headings. 


CHAPTER  II. 

RETINOSCOPE.  —  LIGHT.  —  LIGHT-SCREEN  BRACKET.  — 
DARK  ROOM.— SOURCE  OF  LIGHT  AND  POSITION  OF 
MIRROR. —  OBSERVER  AND  PATIENT.  —  LUMINOUS 
RETINOSCOPE. 

The  Retinoscope,  or  Mirror.— Two  forms  of  the  plane 
mirror  are  in  use — the  one  large,  four  centimeters  in  di- 
ameter, with  a  four-  or  five-millimeter  sight-hole  often  cut 
through  the  glass;  and  the  other  small,  two  centimeters 
in  diameter,  on  a  four-centimeter  metal  disc,  with  sight- 
hole  two  millimeters  in  diameter,  not  cut  through  the  glass, 
the  quicksilver  or  plating  alone  being  removed.  By  thus 
leaving  the  glass  at  the  sight-hole,  additional  reflecting 
surface  is  obtained  at  this  point,  which  assists  materially 
in  exact  work,  as  it  diminishes  the  dark  central  shadow 
that  shows  so  conspicuously  at  times,  and  particularly 
when  the  sight-hole  is  cut  through  the  glass.  The  small 
mirror  has  an  advantage  over  the  large  by  reducing  the 
area  of  reflected  light,  as  only  a  one-centimeter  area  on 
each  side  of  the  sight-hole  is  of  particular  use.  The  small 
plane  mirror^  is  the  one  recommended,  and  is  made  with 
either  a  straight  or  folding  handle  (see  Figs.  2,  3,  4,  18); 
the  latter  is  for  the  purpose  of  protecting  the  mirror  when 
carried  in  the  pocket.  The  purpose  of  the  metal  disc  on 
which  the  small  mirror  is  secured  is  to  keep  the  light  out  of 
the  observer's  eye,  and  enable  him  to  rest  the  instrument 
against  the  brow  and  side  of  the  nose;  but  if  its  size  should 
appear  small,  the  observer  can  easily  have  a  larger  one 
made  to  suit  his  convenience.     The  white  letters  H.  C.  N. 

^Philadelphia  Polyclinic,  November,  1893     Another  form  is  described 
by  Dr.  E.  Jackson,  American  Journal  of  Ophthalmology,  April,  1896. 

•       6 


THE   LIGHT. 


on  the  metal  disc  are  for  the  patient  to  look  at  while  the 
eye  is  being  examined  and  the  lenses  changed  before  his 


Fig. 


-The  Author's  Retinoscopk. 


eye.    The  plating  or  silvering  on  the  mirror  should  be  of 
the  best,  and  free  from  any  flaws  or  imperfections,  for  on 


Fig  3. — Author's  Latest  Model  Retinoscope.  In  Three  Parts. 
(i)  Metal  Disc  and  Handle,  Straight  or  Folding;     (2)  Metal  Back  for  the 
Mirror;    {3)  Plane  Mirror  with  Sight  Hole  made  by  removing  the  Silver- 
ing.    (See  text.) 

its  quaUty  depends,  in  part,  the  good  reflecting  power  of 
the  mirror,  which  is  very  important. 

The  central  shadow  just  referred  to  as  the  result  of  I  he 
sight-hole  had  best  be  seen  by  the  beginner  by  reflecting 

*  See  foot-note  on  preceding  page. 


8 


RETINOSCOPY. 


the  light  from  the  mirror  onto  a  white  surface,  before  he 

begins  any  study,  as  this  dark 
area  may  annoy  him  later  if  he 
does  not  understand  its  origin. 
The  Author's  latest  model 
retinoscope  is  shown  in  Fig.  3. 
This  retinoscope  comes  in 
three  parts,  i-e.,  (i)  the 
metal  disc  and  handle,  (3) 
the  plane  mirror  and  (2)  the 
metal  back  for  the  mirror. 
These  are  put  together  by 
placing  the  mirror  (3)  on  the 
metal  back  (2)  and  then  press- 
ing the  metal  disc  into  the 
opening  of  the  large  metal 
disc  (i).  The  purpose  of 
this  new  model  is  to  supply 
the  oculist  with  any  number 
of  mirrors  in  case  of  breakage 
or  defective  silvering.  The 
handle  (i)  can  be  used  in- 
definitely. Number  (2)  fits 
into  number  (i)  with  great 
accuracy. 

The  Light.— This  should 
be  steady,  clear,  and  white. 
The  Welsbach  possesses  all 
these  qualities,  but  unfor- 
tunately its  delicate  mantle 
will  not  stand  much  jarring, 
and,  as  a  consequence,  is 
^^'  ^'  easily  broken,  causing  much 

loss  of  time  and  annoyance.     The  electric  Kght  made  with 


THE   LIGHT.  9 

a  twisted  carbon  and  ground-glass  covering  having  a  round 
center  of  clear  glass  is  becoming  quite  popular.  For  con- 
stant service,  however,  the  Argand  burner  is  decidedly 
the  best,  when  the  asbestos  light-screen  is  used  to  intercept 
the  heat.  Whatever  light  is  employed,  it  is  well  to  have 
it  on  an  extension  bracket,  so  that  the  observer  may  raise 


Fig. 


or  lower  it  or  move  it  toward  or  away  from  the  patient, 
as  necessary  (see  Fig.  5). 

When  gas  or  electric  Hght  is  not  at  hand,  a  student's 
oil-lamp,  with  a  suitable  light-screen,  will  answer  every 
purpose  (see  Fig.  6). 

The  light-screen,  or  cover  chimney,  is  made  of  one- 
eight  inch  asbestos,  and  of  sufficient  size  (six  centimeters 


lO 


RETINOSCOPY. 


in  diameter  by  twenty-one  in  height)  to  fit  over  the  glass 
chimney  of  the  Argand  burner  (see  Figs.  7  and  8). 

Attached  to  the  screen  are  two  superimposed  revolving 
discs  that  furnish  four  round  openings,  respectively  five, 
ten,  twenty,  and  thirty  millimeters,  any  one  of  which  may 
be  turned  into  place  as  occasion  may  require.  Care  should 
be  taken  that  the  opening  used  is  placed  opposite  to  the 
brightest,  and  never  opposite  to  the  edge  of  the  blue  part 
of  the  flame.  Formerly  these  screens  were  made  of  sheet- 
iron,  but  the  asbestos  has  been  found  preferable,   as  it 


Fig.  6. 


does  not  radiate  the  heat  to  the  same  extent  as  the  iron. 
The  purpose  of  the  light-screen  is  to  cover  all  of  the  flame 
except  the  portion  which  presents  at  the  opening  in  the  disc. 
Figure  8  shows  the  author's  new  Hght-screen,  which  was  de- 
scribed on  page  1378  in  the  "  Journal  of  the  American  Medical 
Association,"  December  3,  1898.  This  is  a  more  conven- 
ient screen  for  retinoscopy  than  the  one  shown  in  Figure  7. 
It  is  made  by  attaching  an  iris  diaphragm  to  an  asbestos 
chimney.  The  amount  of  light  passing  through  the  dia- 
phragm is  easily  controlled  by  an  ivory-tipped  lever  at  the 
left  hand  side;  and  an  index  on  the  periphery  records  the 
diameter  of  the  opening  in  use,  from  one  to  thirty  millimeters. 


THE   SOURCE   OF   LIGHT  AND    POSITION    OF   MIRROR.     II 

Ten-millimeter  Opening. — This  will  be  used  in  most 
all  retinoscopic  work  by  the  beginner. 

Five-millimeter  Opening. — This  is  used  to  the  best 
advantage  and  with  no  small  amount  of  satisfaction  by 
the  expert  when  working  close  to  the  point  of  reversal. 

The  room  must  be  darkened — and  the  darker  the  better; 
all  other  sources  of  light  except  the  one  in  use  should  be 
excluded.  It  must  not  be  supposed  from  this  that  the  room 
must  have  its  walls  and  ceiling  blackened;  on  the  contrary, 
if  the  shades  are  drawn,  the  room  will  be  sufficiently  dark, 
though  of  course  a  room  with  walls  painted  black  or  draped 
in  black  felt  would  be  best,  as  giving  a  greater  contrast 
to  the  condition  to  be  studied.  The  exclusion  of  other 
lights,  or  beams  of  light,  must  be  insisted  upon,  as  the 
principal  use  of  the  darkened  room  is  to  keep  all  light 
except  the  light  in  use  out  of  the  eye  to  be  examined,  and 
also  not  to  have  other  lights  reflected  from  the  mirror. 

As  the  method  of  using  the  concave  mirror  with  source 
of  light  (twenty  or  thirty  mm.  opening  in  screen)  beyond 
its  principal  focus  (usually  over  and  beyond  the  patient's 
head)  has  been  superseded  by  the  simpler  and  easier  method 
of  using  the  small  plane  mirror  with  source  of  light  (one- 
half  or  one  cm.  opening  in  light-screen)  brought  as  close 
to  the  mirror  as  possible,  the  description  of  retinoscopy 
which  follows  will  refer  to  the  latter. 

The  Source  of  Light  and  Position  of  the  Mirror.— 
The  rays  of  Hght  coming  out  of  the  round  opening  in  the 
light-screen  should  be  five  or  six  inches  to  the  left  and  front 
of  the  observer,  so  that  they  may  pass  in  front  of  the  left 
eye  and  fall  upon  the  mirror  held  before  the  right,  thus 
leaving  the  observer's  left  eye  in  comparative  darkness; 
or  the  observer  may  use  the  mirror  before  the  left  eye  in 
case  he  is  left-handed  and  has  the  light  to  his  right.  It  is 
always  best  for  the  observer  to  keep  both  eyes  wide  open 


12 


RETINOSCOPY. 


and  to  avoid  having  any  light  fall  into  the  unused  eye, 
which  would  cause  him  much  annoyance.  Some  observers 
hold  the  mirror  before  the  eye  next  to  the  screen,  but  this 
is  not  recommended,  for  the  reasons  just  mentioned. 

The  observer  need  not  make  any  note  of  his  accom- 
modation, as  in  using  the  ophthalmoscope,  but,  as  he 
requires  very  acute  vision,  he  should  wear  any  necessary 
correcting   glasses.     Any   observer  whose   vision   does  not 


Fig.  7. — THE  Auihor's  Light- 
screen,  OR  Cover  Chimney. 
(For  a  further  description,  see  Chap.  VI.) 


Fig.  8. 


-The  Author's  K  ew  Light- 
screen. 


approximate  f  in  the  eye  which  he  uses  will  not  get  much 
satisfaction  from  retinoscopy. 

He  should  take  his  seat  facing  the  patient,  and,  as  the 
strength  or  brilliancy  of  the  reflected  light  rapidly  weakens 
as  the  distance  between  the  mirror  and  the  light-screen 
is  increased,  he  should  have  the  light-screen  close  to  his 
face  (not  farther  away  than  six  inches)  if  he  wishes  to  get 
the  fullest  possible  strength  of  light  on  the  mirror. 


THE    SOURCE    OF   LIGHT  AND   POSITION   OF   MIRROR.    1 3 

As  the  light  appears  just  as  far  back  in  the  mirror  as  it 
is  in  front  of  it,  then  the  nearer  these  two  objects  are  brought 
together,  the  more  nearly  do  they  become  as  one.     When 


^^^ 


Fig.  9 


Fig.  10. 


working  close  to  the  point  of  reversal,  more  exact  work 
will  be  accomplished  if  this  distance  between  the  light  and 
mirror  is  very  short.  The  nearer  together  the  light  and 
mirror,  the  brighter  the  retinal  illumination,  and  greater 


14  RETINOSCOPY. 

contrast,  or  sharper  cut  edge  between  illumination  and 
surrounding  shadow.  The  further  the  light  from  the  mirror, 
the  dimmer  the  retinal  illumination,  and  there  will  appear, 
under  certain  conditions,  a  very  conspicuous  central  shadow 
as  the  result  of  the  sight-hole  in  the  mirror — two  very  seri- 
ous objections. 

^-  The  Luminous  Retinoscope  (Figs.  9  and  10).  — DeZeng 
Patent. — This  instrument  is  the  author's  plane  mirror  with 
the  electric  Hght  attachment.  A  5 -volt  electric  Hght  with 
tiny  filament  is  contained  in  a  tube  placed  at  an  angle  of 
45  degrees  with  the  handle,  and  the  mirror  is  correspond- 
ingly tilted  to  an  angle  of  22  degrees.  The  Hght  from  the 
filament  passes  divergently  to  a  strong  convex  lens  which 
renders  the  rays  less  divergent  as  they  fall  upon  the  mirror, 
and  from  the  mirror  the  rays  pass  divergently  to  the  patient's 
eye.  (Fig.  10.)  This  instrument  has  innumerable  points 
of  merit:  It  does  away  with  any  use  of  gas  or  lamp  or 
cover  chimney;  the  observer  is  not  annoyed  with  the  heat 
from  the  gas  or  lamp;  the  observer  does  not  have  to  move 
the  light  or  bracket  when  changing  from  one  distance  to 
another  as  when  working  with  the  gas-light  close  to  the 
mirror;  the  electric  wires  (cords)  carrying  the  current 
to  the  filament  are  of  sufficient  length  to  give  the  observer 
two  meters  of  space  in  which  to  practice  the  method;  the 
brilliancy  of  the  illumination  can  be  made  most  intense  or 
diminished  very  materially  with  a  convenient  rheostat; 
the  size  of  the  divergent  pencil  may  be  controlled  by  adjust- 
ing the  condensing  lens  at  the  end  of  the  tube.  The  writer 
is  in  the  habit  of  using  the  mirror  and  gas  flame  until  he 
has  obtained  an  approximate  point  of  reversal  and  then 
substitutes  the  luminous  instrument  to  obtain  the  more 
delicate  findings;  he  does  this  for  the  reason  that  if  the 
electric  light  is  used  for  any  great  length  of  time  to  find 
the  point  of  reversal  a  temporary  scotoma    is    produced 


THE    LUMINOUS   RETINOSCOPE. 


15 


that  some  nervous  patients  occasionally  object  to.  This 
luminous  instrument  will  also  bring  to  the  notice  of  the 
careful  observer  some  fine  changes  in  the  lens  fibers  if 
present,  that  he  might  otherwise  overlook. 

The  DeZeng  Ideal  Electric  Retinoscope  (Fig.  n). — This 
instrument  does  away  with  electric  wires,  therefore  giving  it 
portability.  The  handle  is  made  of  aluminum  and  designed 
to  hold  a  two- cell  battery  of  regular  stock  size. 
This  handle  is  convenient  to  hold  and  has 
a  compressible  circuit  breaker  conveniently 
located  for  the  thumb  of  the  operator.  It  is 
arranged  for  either  a  touch  or  a  fixing  contact, 
the  lamp  being  lighted  either  by  pressing  the 
extending  arm  against  the  handle  or  swinging 
it  around  in  contact  with  the  clip  on  the  top 
of  the  cap  as  desired. 

The   mirror   is   the  author's  small   plane 
mirror  with  sighthole  made  by  removing  the 
silvering  only.     The  Fixation  Letters  on  the 
disc  are  those  suggested  and  described  in  the 
Author's  work  ''  Refraction  and  How  to  Re- 
fract."     These    letters    are    quite    cleverly 
illuminated    by    the    light    from    the    lamp 
passing    through    an   opening   in   the   tube. 
Tiny  Tungsten  lamps  are  supplied  for  this 
retinoscope. 
\       ^The  patient  must  have  his  accommodation 
thoroughly  relaxed  with  a  reliable  cycloplegic, 
I     and  should  be  seated  comfortably,  one  meter 
1     distant,  in  front  of  the  observer,  with  his  vision  steadily 
1    fixed  on  the  observer's  forehead,  just   above  the  mirror. 
j     Or,  what  is  even  better,  the  patient  may  concentrate  his 
vision  on  the  letters  at  the  edge  of  the  metal  disc  of  the 
mirror  (Figs.  3,  4,  11)  or  on  the  observer's  forehead,  but 


Fig.  II.— 
The  DeZeng 
Ideal  Elec- 
tric Retino- 
scope. 


/ 


1 6  RETINOSCOPY. 

never  directly  into  the  mirror,  as  that  would  soon  irritate 
and  compel  him  to  close  his  eye. 

In  this  way  the  patient  avoids  the  strain  of  looking  into 
the  bright  reflexed  light,  and  at  the  same  time  the  macular 
region  is  refracted  (see  Fig.  32).  It  is  customary  to  cover 
the  patient's  other  eye  while  its  fellow  is  being  refracted; 
for  obvious  reasons  this  is  specially  important  in  cases  of 
"squint."  The  axonometer  placed  before  the  eye  being 
examined  is  a  decided  advantage  in  any  instance  (see  p.  52 
and  Fig.  44). 


CHAPTER  III. 

DISTANCE  OF  SURGEON  FROM  PATIENT.— ARRANGEMENT 
OF  PATIENT,  LIGHT,  AND  OBSERVER.— REFLECTION 
FROM  MIRROR.— HOW  TO  USE  THE  MIRROR.— WHAT 
THE  OBSERVER  SEES.— RETINAL  ILLUMINATION.— 
SHADOW.— WHERE  TO  LOOK  AND  WHAT  TO  LOOK 
FOR. 

Distance  of  Surgeon  from  Patient. — There  is  no 
fixed  rule  for  this,  and  each  surgeon  may  select  his  own 
distance.  It  might  be  well  for  the  beginner  to  try  different 
distances  and  then  choose  for  himself.  The  writer  prefers 
a  one-meter  distance,  and  with  few  exceptions  adheres 
to  it.  Some  prefer  six  meters,  others  two  meters,  etc. 
The  distance  of  one  meter  has  important  advantages: 
There  is  no  necessity  for  getting  up  to  place  lenses  in  front 
of  the  patient's  eye,  as  the  patient  or  surgeon,  or  both,  may 
lean  forward  for  this  purpose,  if  necessary.  Another  ad- 
vantage is  that  at  one-meter  distance  there  is  a  uniform 
allowance  of  one  diopter  in  the  estimate,  which  will  be 
explained  more  fully  under  Rules  for  Retinoscopy  at  One 
Meter.  To  get  the  patient's  eye  and  the  observer's  forehead 
just  one  meter  apart,  the  distance  may  be  marked  off  on  the 
wall  qJ  the  dark  room  on  the  side  where  the  light  is  secured 
(see  Fig.  13),  or  a  meter  stick  for  the  purpose  may  be  held 
in  the  hand  of  the  observer  or  his  assistant. 

The  method  of  obtaining  the  point  of  reversal  at  points 
other  than  the  regulation  one  meter  requires  such  an 
amount  of  extra  measuring  and  computing  that  it  does  not 
meet  with  the  general  favor  and  satisfaction  accorded 
to  that  found  by  producing  an  artificial  myopia  of  one 
diopter.     This  can  best  be  explained  by  reference  to  Figure 

2  17 


RETINOSCOPY. 


52 

0.75 

45 

0.87 

40 

I.P 

35 

1.12  D 

31.5 

I25D 

26.25 

I.50D 

22.5 

1.75  D 

20 

2.3 

.750 

2.25D 

15.75 

2.50 

13 

275 
3.B 

25 

3.50D 

10 

4.D 

873 

4sn 

a 

sn 

7 

550  D 

6     "  ,-   ■ 

6.506, „       ^° 

.   s^5-5fc= 

^   7D7SO  ,,  n 

12,  where,  if  the  observer  is  at  one- 
meter  distance,  and  the  neutrahzing 
lens  in  front  of  the  patient's  eye 
focuses  the  emergent  rays  about  that 
distance,  he  may  have  the  liberty  of 
moving  forward  or  back  five  inches  (a 
play  of  ten  inches)  in  looking  for  the 
point  of  reversal,  and  not  make  a 
possible  error  in  his  result  of  more 
than  twelve  one-hundredths  (0.12)  of 
a  diopter;  whereas  if  he  was  working 
closer  than  this,  say  at  half  a  meter, 
and  was  moved  forward  or  backward 
five  inches  to  find  the  point  of  reversal, 
he  would  likely  make  an  error  of  0.5 
D.,  or  even  more,  if  he  was  not  ex- 
tremely careful  in  measuring  the  dis- 
tance at  which  he  found  the  reversal 
point. 

Arrangement  of  Patient,  Light, 
and  Observer. — This  has  already 
been  described  in  great  part,  but  refer- 
ence to  the  accompanying  sketch  may 
give  the  student  a  more  exact  apprecia- 
tion of  the  arrangement  than  any 
lengthy  description  could  do. 

For  the  convenience  of  the  beginner 
in  using  the  mirror,  it  is  best,  as  here 
shown,  to  keep  the  surgeon's  eye,  the 
Hght,  and  the  patient's  eye  on  a  hori- 
zontal line,  and  to  accompHsh  this  in 
children  they  will  either  have  to  stand; 
sit  on  a  high  stool,  or  on  the  parent's 
lap.     The  beginner  will  find  it  suffi- 


ARRANGEMENT  OF  PATIENT,  LIGHT,  AND  OBSERVER.  1 9 

ciently  difficult  at  first  to  reflect  and  keep  the  light  on 
the  patient's  eye  with  the  mirror  held  perpendicularly,  with- 
out inclining  it  up  or  down,  as  he  would  have  to  do  if  the 
arrangement  suggested  is  not  carried  out.  Placing  the 
hght  to  one  side  of  the  patient's  head,  or  above  it  (Fig.  14), 
and  the  observer  seated  at  one-meter  distance  from  the 
patient,  is  a  convenient  way  of  working  retinoscopy.     It  has 


Fig.  13. — Arrangeaiext  of  Patiext,  Light  axd  Oculist. 

two  advantages:  the  observer  avoids  the  heat  of  the  flame, 
and  at  the  same  time  does  not  have  to  move  the  light.  But 
the  writer  is  not  partial  to  this  mode  of  procedure,  for 
various  reasons  of  precision,  explained  in  the  text. 

Reflection  from  the  Mirror. — The  rays  of  light  coming 
from  the  round  opening  in  the  screen  to  the  p'ane  mirror 
are  reflected  divergently,  as  if  they  came  from  the  opening 
in  the  screen  situated  just  as  far  back  in  the  mirror  as  they 
originally  started  from  in  front  (see  Figs.  29,  31  and  ^;^), 


20 


RETINOSCOPY. 


and  the  patient,  looking  into  the  mirror,  sees  a  round, 
bright  spot  of  light,  corresponding  to  the  opening  in  the 
screen.     Fig.  i8. 

How  to  Use  the  Mirror.— It  should  be  held  firmly 
before  the  right  eye  (Figs.  15  and  16)  so  that  the  sight-hole 
is  opposite  to  the  observer's  pupil;  and  that  it  may  be  steady, 
the  second  phalanx  of  the  thumb  should  rest  on  the  cheek 


Fig.  14. — Light  above  Patient's  Head  and  Oculist  at  One  Meter 
Distance. 

just  below  the  eye,  the  edge  of  the  metal  disc  even  touching 
the  side  of  the  nose  if  the  observer's  inter  pupillary  distance 
is  not  too  great.  Thus  held  in  position,  its  movements 
should  be  very  limited,  though  they  may  be  slow  or  quick, 
but  never,  at  any  time,  should  it  be  tilted  more  than  one, 
two,  or  even  three  millimeters;  for  if  inclined  more  than  this 
the  Hght  is  lost  from  the  pat'ent's  eye.  If  the  Hght,  the 
patient's,  and  the  observer's  eyes  are  on  a  horizontal  line, 


HOW   TO    USE    THE   MIRROR.  21 

then  to  find  the  patient's  eye  with  the  reflected  light  all  the 
observer  has  to  do  is  to  reflect  the  light  back  into  the  light- 
screen,  and  by  rotating  the  mirror  to  his  right,  carry  the 
reflected  light  around  on  the  same  horizontal  line  until 
the  patient's  eye  is  reached.  This  may  seem  like  a  super- 
abundance of  instruction,  but  the  finding  of  the  patient's 


Fig.  15.— Mirror  Held  Correctly   before    Right  Eye  and  Oculist 
Keeps  Both  Eyes  Open. 

eye,  which  appears  so  easy,  is  an  immense  stumbUng-block, 
at  the  beginning,  to  most  students.  Another  way  to  find 
the  eye  is  for  the  observer  to  hold  his  left  hand  up  between 
his  and  the  patient's  eye  and  reflect  the  Hght  on  to  it,  and 
when  this  is  done  to  drop  his  hand  and  let  the  light  pass  into 
the  observed  eye.  Having  succeeded  in  finding  the  patient's 
eye,  the  observer,  if  he  is  not  very  careful  in  his  limited 


22 


RETINOSCOPY. 


movements  of  the  mirror  and  himself,  will  turn  the  light 
from  the  eye  almost  before  he  knows  it,  and  so  be  compelled 
to  start  and  find  it  again;  this  causes  much  loss  of  time.  A 
little  practice  on  the  schematic  eye  will  assist  the  beginner 
wonderfully  and  give  him  courage,  for  if  he  hastens  to  the 
human  eye,  and  then  has  to  stop  every  minute  or  so  to  try 


Fig.  i6. — Correct  Position  for  Mirror  but  there  is  no  Necessity 
FOR  THE  Oculist  to  Squeeze  the  Left  Eye  Shut  after  having  Lo- 
cated THE  Patient's  Eye. 


and  get  the  light  on  the  eye,  he  soon  becomes  discouraged 
and  shows  his  war^t  of  experience  to  the  patient. 

What  the  Observer  Sees  or  the  General  Appearance 
of  the  Reflection  from  the  Eye. — With  the  mirror  held  before 
his  eye,  and  close  up  to  the  bright  light  coming  from  the 
ten-millimeter  opening  in  the  light-screen,  the  observer 
will  obtain   a  reflection   from   the  pupillary   area   of  the 


HOW    TO    USE    THE    MIRROR. 


23 


patient's  eye  which  varies  in  different  patients,  and  is 
subject  to  certain  changes  in  the  same  patient  as  the  refrac- 
tion is  altered  by  correcting  lenses,  or  it  may  be  changed  by 
the  turning  of  the  patient's  eye,  or  lengthening  the  dis- 
tance between  the  mirror  and  the  light,  or  increasing  or 
diminishing  the  strength  of  the  light,   or  increasing  the 


Fig.  17.  Fig.  18. 

Author's  Mirror  with  Folding  Handle. 
Fig.  17. — Showing  central  light  C,  on  small  mirror  B.     This  is  the  lighi 
the  patient  sees  when  looking  into  the  mirror,  and  corresponds  in  size 
to  the  one-centimeter  opening  in  screen.     D  is  the  folding  cap  handle 
to  protect  B  when  not  in  use.     A  is  the  metal  disc. 
Fig.  18. — Shows  the  light  moved  to  one  side  as  a  result  of  tilting  the  mirror. 

distance  between  the  observer  and  the  patient.  The 
reflection  from  the  eye  of  the  albino  or  blond  is  much 
brighter  than  from  the  brunette  or  mulatto,  in  whom  it  is 
not  so  bright,  even  dim.  This  character  of  the  reflex  is 
controlled,  of  course,  in  great  part  by  the  amount  of  pig- 
ment in  the  eye  ground;  however,  in  most  instances,  there 
is  more  or  less  of  a  yellowish-red  color  to  the  reflex,  and  this 


\ 


24  RETINOSCOPY. 

is  especially  so  as  the  point  of  reversal  is  approached;  at  the 
point  of  reversal,  however,  the  reflex  becomes  less  brilliant 
and  possesses  something  of  the  color  of  a  piece  of  newly 
coined  silver.  Cases  of  high  errors  of  refraction  give  a 
dull  reflex  (see  Fig.  27)  as  compared  to  low  errors,  where 
the  reflex  is  usually 'z;er>' bright  (see  Fig.  19).  Should  the 
media  be  irregular  or  not  perfectly  clear,  the  reflex  is  altered 
accordingly;  this  will  be  referred  to  under  the  head  of 
Irregular  Astigmatism.  The  observer  will  also  notice 
on  the  cornea  and  lens  bright  pin-point  catoptric  images, 
and  at  the  inner  edge  of  the  iris,  in  many  eyes,  a  very  bright 
ring  of  Hght  (see  Fig.  19)  about  one  millimeter  in  width, 
which  is  due  to  the  very  strong  peripheral  refraction;  and 
as  the  eye  is  being  refracted  and  the  point  of  reversal  ap- 
proached, this  peripheral  ring  may  develop  into  a  broader 
ring  of  aberration  rays,  which  at  times  will  be  annoying. 
This  will  be  referred  to  under  Spheric  Aberration,  Chap- 
ter VI. 

Retinal   Illumination. — By  holding  a   strong  convex 
lens  closer  to  or  further  from  a  plane  surface  than  its 


# 


P'iG.  19.  Fig.  20. 

Fig.  19. — Uniform  Illumination  in  an  Emmetropic  Eye  with  Slight 

Spheric  Aberration. 
Fig.  20. — Uniform  Illumination  as  in  Fig.  13   passed  to  the  Left  by 
rotating  the  Mirror,  Darkness  or  Shadow  Following. 

principal  focus,  or  at  the  distance  of  its  principal  focus, 
and  letting  the  sun's  rays  pass  through  it,  there  will  be  seen 
on  the  plane  surface  a  round  area  of  light;  it  is  this  light 
area  which  corresponds  to  the  illumination  on  the  retina, 
seen  in  retinoscopy  by  reflecting  the  light  from  the  mirror 


SHADOW.  25 

into  the  patient's  eye,  and  hence  it  is  spoken  of  as  the  retinal 
illumination,  the  "illuminated  area,"  *'the  area  of  light," 
"the  image,"  etc. 

Of  course,  the  form  of  this  illumination  is  controlled, 
in  great  part,  by  the  refraction  of  the  patient's  eye. 

Shadow. — This  is  the  non-illuminated  portion  of  the 
retina  immediately  surrounding  the  illumination.  The 
retinal  illumination  and  shadow  are,  therefore,  in  contact, 
and  the  contrast  is  most  marked  and  easily  recognized 
when  the  refractive  error  is  a  moderately  high  one,  two 
or  three  diopters.  It  is  by  this  combination  of  the  illu- 
mination and  non-illumination  (shadow)  that  we  study 
and  give  the  ''shadow  test"  its  name.  In  the  dark  room, 
the  patient  keeping  his  eye  fixed,  the  retina  is  stationary 
and  in  total  darkness,  except  the  portion  illuminated  by 
the  light  from  the  mirror  (see  Fig.  19).  If  the  mirror  be 
tilted  the  retinal  illumination  changes  its  place  (see  Fig. 
20)  and  darkness,  or  shadow,  appears  in  its  stead.  It  is 
by  this  change  of  shadow  (darkness)  for  illumination  that 
we  often  speak  of  a  movement  of  the  shadow. 

Where  to  Look  and  What  to  Look  For.— With  the 
patient,  the  observer,  and  the  source  of  light  in  position 
as  directed,  the  rays  of  light  are  reflected  into  the  eye  from 
the  mirror  as  it  is  gently  tilted  in  various  meridians,  and 
the  (i)  form,  (2)  direction,  and  (3)  rate  of  movement  of  the 
retinal  illumination  are  carefully  noted  through  a  four-  or 
five-millimeter  area  at  the  apex  of  the  cornea,  as  this  is  the 
part  of  the  refractive  media  in  the  normal  eye  that  the 
patient  will  use  when  the  effects  of  the  cycloplegic  pass 
away  and  the  pupil  regains  its  normal  size. 

The  one-  or  two-millimeter  area  at  the  edge  of  the  pupil 
should  be  avoided  by  the  beginner,  except  in  special  in- 
stances, as  only  too  frequently  it  contains  a  bright  ring  of 
light  which  may  or  may  not  give  a  stronger  refraction  than 


/ 


26  RETINOSCOPY. 

the  4-millimeter  area  about  the  apex  of  the  cornea  (see 
Spheric  Aberration,  Chap.  VI). 

The  beginner  will  do  good  work  with  the  retinoscope 
if  he  observes  closely  the  illumination  at  the  center  of  the 
pupil  and  avoids  looking  for  shadows. 


J 


CHAPTER  IV. 

POINT  OF  REVERSAL.— TO  FIND  THE  POINT  OF  REVER- 
SAL.—WHAT  TO  AVOID.— DIRECTION  OF  MOVEMENT 
OF  RETINAL  ILLUMINATION.— RATE  OF  MOVEMENT 
AND  FORM  OF  ILLUMINATION.— RULES  FOR  LENSES. 
—MOVEMENT  OF  MIRROR  AND  APPARATUS. 

Point  of  Reversal. — This  may  be  defined  in  several 
ways — namely:     It  is  the  far-point  of  a  myopic  eye,  or 
The  artificial  focal  point  of  the  emergent  rays  of  light 

(Fig.  30),  or 
The  point  where   the   emergent  rays   cease   to   converge 

and  commence  to  diverge,  or 
The  point  conjugate  to  a  point  on  the  retina  (Fig.  34),  or 
The  point  where  the  erect  image  ceases  and  the  inverted 

image  begins,  or 
The  point  distant  from  the  eye  under  examination,  where 

the  retinal  illumination  cannot  be  seen  to  move,  when 

the  mirror  is  being  tilted. 
The  point  of  magnification. 

To  Find  the  Point  of  Reversal. — The  recognition  of 
the  point  of  reversal  is  the  principle  of  retinoscopy.  It 
is  what  is  sought  for,  and,  when  obtained  under  certain 
definite  arrangements,  is  the  correct  solution  of  the  test. 
During  the  test  it  is  easy  to  tell  when  the  illumination 
moves  with  or  opposite  to  the  movement  of  the  light  on 
the  face,  but  to  get  the  exact  point  where  there  is  no  apparent 
movement  is  not  always  easy,  and  the  ability  to  quickly 
find  this  point  of  reversal  is  only  acquired  after  careful 
practice. 

For  example,  having  determined  at  one  meter  that' the 
retinal  illumination  with  a  + 1.50  D.  in  front  of  the  observed 

27 


28  RETINOSCOPY. 

eye  just  moves  with  the  Hght  on  the  face,  and  against  with 
a  +1.75  D.,  we  know  that  the  reversal  point  must  be  ob- 
tained with  the  lens  numbered  between  the  strength  of 
these  two  lenses,  i.e.,  + 1.62  D.  This  demonstrates  how  we 
arrive  at  the  exact  correction,  and  also  the  capability  and 
accuracy  of  retinoscopy. 

Emmetropic  and  hyperopic  eyes,  in  a  state  of  rest,  emit 
parallel  and  divergent  rays,  respectively,  and  to  give  such 
eyes  a  point  of  reversal,  or  a  focus  for  the  emergent  rays, 
it  will  be  necessary  to  intercept  these  rays  with  a  convex 
lens  as  they  leave  the  eye.  In  other  words,  emmetropic 
and  hyperopic  eyes  must  be  made  (artificially)  myopic. 
In  myopic  eyes,  however,  the  emergent  rays  always  focus  at 
some  point  inside  of  infinity,  and  the  observer  may,  there- 
fore, if  he  is  so  disposed,  by  moving  his  light  and  mirror 
toward  or  away  from  the  patient's  eye,  as  the  case  may  be, 
find  a  point  where  the  retinal  illumination  ceases  to  move. 
If  this  should  be  at  two  meters,  the  patient  would  have  a 
myopia  of  0.50  D.;  if  at  four  meters,  a  myopia  of  0.25  D.; 
if  at  one  meter,  a  myopia  of  one  diopter,  if  at  half  a  meter, 
a  myopia  of  two  diopters,  if  at  ten  inches,  a  myopia  of  four 
diopters,  etc. 

It  is  well  for  the  beginner  to  remember,  when  using 
the  plane  mirror,  that  the  illumination  on  the  patient^ s  face 
always  moves  in  the  same  direction  the  mirror  is  tilted,  but 
not  necessarily  so  in  the  pupillary  area,  where  it  may  ap- 
pear to  move  opposite;  and  here  it  is  that  we  speak  of  the 
retinal  illumination  moving  with  or  against  (opposite  to) 
the  movement  of  the  mirror,  as  the  case  may  be,  and  make 
our  diagnosis  accordingly. 

As  the  rays  of  light  from  the  mirror  proceed  divergently 
to  the  patient's  eye,  as  if  they  came  from  a  point  back  in 
the  mirror  equal  to  the  distance  of  the  light  (opening  in 
light-screen)   in  front  of  it  and  working  at  one  metre's 


TO   FIND   THE   POINT    OF   REVERSAL.  29 

distance,  with  source  of  light  five  inches  in  front  of  the 
mirror,  the  rays  appear  to  emerge  from  a  point  five  inches 
back  of  the  mirror,  or  a  total  distance  of  45  inches  from 
the  patient's  eye,  thus  giving  the  rays  of  light  a  diver- 
gence equal  to  0.87  of  a  diopter  before  they  reach  the 
patient's  eye,  and  this  point  may  be  made  conjugate  to  the 
retina.  The  observer  will  do  good  work  if  he  reduces  the 
retinal  illumination  to  the  utmost  limit  where  it  can  be 
faintly  seen  moving  with  the  movement  of  the  mirror, 
and  if  this  is  done,  the  observer's  eye  and  mirror  will  be 
just  inside  of  the  point  of  reversal  where  the  erect  image 
can  still  be  recognized.  In  doing  this,  however,  he  must 
allow  0.87  in  his  estimate  and  not  i.oo  D. 

At  the  point  of  reversal  no  definite  movement  of  the 
retinal  illumination  is  made  out  and  the  pupillary  area  is 
seen  to  be  uniformly  illuminated,  but  not  so  brilliantly 
as  when  within  or  beyond  the  point  of  reversal. 

If  the  observer's  eye  is,  at  this  point,  exactly  conjugate 
to  the  retina,  then  the  movement  of  the  reflected  light  on 
the  retina  cannot  be  perceived  (though  it  does  move), 
and  the  retinal  illumination  will  occupy  the  entire  pupil 
and  the  shadow  will  be  absent. 

Instead,  however,  of  reducing  the  retinal  illumination 
to  the  utmost  limit  (as  just  mentioned),  where  it  can  be 
faintly  seen  moving  with  the  movement  of  the  mirror, 
the  writer  prefers  and  recommends  placing  before  the  eye 
under  examination  such  a  lens  or  series  of  lenses  that  will 
bring  the  emergent  rays  of  light  to  a  focus  on  his  own 
retina,  so  that  no  movement  of  the  retinal  illumination  can 
be  recognized. 

When  the  point  of  reversal  is  approached,  the  uniform 
color  of  the  retinal  illumination  occupies  so  much  of  the 
pupillary  area  that  the  student  may  think  he  has  reached 
the  point  of  reversal,  and  if  he  is  not  careful  to  pass  the 


3©  RETINOSCOPY. 

retinal  illumination  slowly  across  the  pupil  and  get  the 
shadow,  he  will  find  his  result  deficient,  and  possibly  may 
also  fail  to  recognize  or  may  miss  seeing  some  small  amount 
of  astigmatism. 

To  make  sure  that  the  point  of  reversal  has  been  obtained, 
it  is  always  best,  especially  for  the  beginner,  to  keep  putting 
on  stronger  neutraHzing  lenses  until  he  gets  a  reversal  of 
movement,  when  he  knows  at  once  that  the  point  of  focus 
of  the  emergent  rays  has  passed  in  between  the  mirror 
and  eye  under  examination. 

The  lenses  which  control  the  rays  of  light  emerging 
from  the  patient's  eye  are  spoken  of  as  neutraHzing  lenses. 

What  to  Avoid. — It  occasionally  happens  that  a  retinal 
vessel  or  vessels  or  a  remnant  of  a  hyaloid  artery,  if  present, 
or  even  the  nerve  head,  may  be  seen  when  the  light  is 
reflected  into  the  eye;  if  so,  they  are  to  be  ignored,  as  they 
are  not  parts  of  the  test.  If  the  patient's  eye  is  turned, 
or  the  rays  from  the  mirror  fall  obliquely,  or  the  neutral- 
izing lens  in  front  of  the  eye  is  incHned  instead  of  being 
perpendicular,  there  will  be  seen  reflections  of  light  and 
images  upon  the  neutralizing  lens  or  cornea,  or  both,  and, 
in  consequence,  the  retinal  illumination  is  more  or  less 
hidden  or  obscured;  these  images  and  reflections  can  be 
easily  corrected  by  removing  the  cause.  The  catoptric 
images  cannot  be  removed,  but  as  they  are  very  small, 
the  beginner  soon  learns  to  ignore  them.  The  retinal 
illumination  may  occasionally  contain  a  small  dark  center, 
which  will  disturb  the  beginner  unless  he  remembers  that 
it  is  caused  by  the  sight-hole  in  the  mirror,  and  is  most 
likely  to  occur  when  the  sight-hole  is  large  and  cut  through 
the  mirror.  This  same  dark  center  in  the  illumination  is 
also  seen  at  times  when  the  light  is  removed  some  distance 
from  the  mirror,  and  the  correcting  lens  almost  neutralizes 
the  refraction.     The  neutralizing  lens  should  never  be  so 


FORM   OF   ILLUMINATION.  3 1 

close  to  the  eye  that  the  lashes  touch,  and,  in  warm  weather 
especially,  moisture  from  the  patient's  face  may  condense 
on  the  trial-lens,  and  temporarily,  until  it  is  removed, 
obscure  the  reflex. 

Retinoscopy  with  a  Plane  Mirror  at  One  Meter's 
Distance  and  Source  of  Light  Close  to  the  Mirror. — 
Direction  of  Movement  of  Retinal  Illumination. — 
Apparent  Rate  of  Movement  and  Form  of  Illimiination. 
— These  important  points  in  reference  to  the  retinal  illumi- 
nation should  be  decided  promptly  and  without  any  pro- 
longed examination.  This  proficiency,  of  course,  will  only 
come  by  practice,  and  if,  on  first  examination,  the  observer 
cannot  decide  whether  the  retinal  illumination  is  moving 
with  or  opposite  to  the  movement  of  the  reflected  Hght  on  the 
face,  he  may  approach  the  eye  until  this  point  is  deter 
mined.  At  the  distance  of  one  meter  the  three  important 
essentials  may  be  stated  in  the  following  order  and  in  the 
form  of  rules: 

Direction  of  Movement  of  Retinal  Illumination. — 
The  recognition  of  the  direction  that  the  retinal  illumina 
tion  takes  when  tilting  the  mirror  is  a  most  important  point 
in  the  study  of  retinoscopy. 

The  movement  of  the  retinal  illumination,  when  rotating 
the  mirror,  going  with  the  movement  of  the  light  on  the 
patient's  face,  signifies  emmetropia,  hyperopia,  or  myopia, 
if  the  myopia  is  less  than  one  diopter. 

The  apparent  movement  of  the  retinal  illumination  going 
opposite  to  the  movement  of  the  light  on  the  face  always 
signifies  myopia  of  more  than  one  diopter. 

Rate  of  Movement. — This,  of  course,  is  imder  the 
control  and  is  influenced  in  great  part  by  the  rate  of  move- 
ment of  the  mirror  itself;  yet  after  a  little  practice  the 
observer  will  recognize  the  fact  that  there  is  a  certain 
slowness  in  the  apparent  rate  of  movement  of  the  illumi- 


/ 


32  RETINOSCOPY. 

nation  when  the  refractive  error  is  a  high  one  and  requires 
a  strong  lens  for  its  neutralization,  whereas  when  the  ret- 
inal illumination  appears  to  move  fast,  the  refractive  error 
is  bu  slight,  and  requires  a  weak  lens  for  its  correction. 

Form  of  Illumination. — A  large,  round  illumination, 
while  it  may  signify  hyperopia  or  myopia  alone,  yet  it 
does  not  preclude  astigmatism  in  combination. 

When  the  illumination  appears  to  move  faster  in  one 
meridian  than  the  meridian  at  right  angles  to  it,  astig- 
matism will  be  in  the  meridian  of  slow  movement.  If  the 
retinal  illumination  is  a  band  of  light  extending  across 
the  pupil,  it  signifies  astigmatism. 

The  width  of  the  band  of  light  does  not  indicate  so 


Fig.  21. — Straight  Edge,  Indicat-    Fig.  22. — Crescent  Edge,  Indicat- 
ing Astigmatism.  ing  Spheric  Correction. 

much  the  strength  of  the  correcting  cylinder  required  for 
its  neutralization  as  does  the  apparent  rate  of  movement; 
if  slow,  a  strong,  if  fast,  a  weak,  cylinder  is  required. 

The  meridian  subtended  by  the  band  of  light  that  is  seen 
when  a  spheric  lens  of  one  diopter  or  more  corrects  one  meri- 
dian and  the  meridian  at  right  angles  remains  partly  cor- 
rected, indicates  the  axis  of  the  cylinder  in  the  prescription. 

Rules  for  Placing  Neutralizing  Lenses.— A  plus  lens 
is  required  when  the  retinal  illumination  moves  with  the 
illumination  on  the  face,  and  a  minus  lens  is  required  when 
it  moves  opposite  to  the  light  on  the  ^ace. 

Movement  of  the  Mirror. — There  are  times  when 
a  quick  movement  of  the  mirror,  and,  at  other  times,  a  slow 


MOVEMENTS    OF   THE   MIRROR. 


33 


#-# 


or  gradual  movement  is  required.  A  substitution  of  the 
quick  when  the  slow  movement  is  necessary,  then  the 
refraction  cannot  always  be  accurately  determined.  This 
is  explained  under  "slow  movement." 

A  quick  movement  of  the  mirror  may  be  used  when 
looking  into  the  eye  before  any  correcting  lens  has  been 
placed  in  situ.     It  often  tells  the  character 
of  the  refraction. 

The  slow  movement  of  the  mirror  and 
the  five-millimeter  opening  in  light-screen 
come  into  use  and  are  of  the  utmost  impor- 
tance when  the  eye  has  been  corrected  to 
within  0.75  D.  or  less,  as  it  is  generally  at 
this  point  that  so  many,  by  a  quick  move- 
ment, hasten  the  peripheral  rays  and  mask 
the  central  illumination,  giving  the  idea  at 
once  of  over-correction  (see  Spheric  Aber- 
ration, Chap.  VI).  This  is  a  most  com- 
mon error  with  the  beginner,  the  inexperi- 
enced, and  with  those  who  fail  to  get  good 
results  and  who  ridicule  retinoscopy  as  "not 
exact,"  or  as  "not  agreeing  with  the  sub- 
jective method."  It  is  well  in  every  in- 
stance, when  the  point  of  reversal  is  ap- 
proached, to  pass  the  retinal  illumination 
(not  the  light  area  on  the  face)  well  across 
the  pupillary  area  to  make  sure  in  regard 
to  the  character  of  shadow  which  follows 
or  precedes  it.  This  movement,  at  such 
a  point  in  neutralization,  will  often  give  a  hint  as  to  the 
presence  of  astigmatism  or  not,  as  a  reference  to  Figures 
21  and  22  will  show.  The  presence  of  astigmatism  is 
known  by  the  straight  edge  of  the  illumination,  or,  in  its 
place,  a  crescent  edge  would  mean  a  spheric  correction. 
3 


Fig.  32.— WUrde- 
mann's  Disc. 


34  RETINOSCOPY. 

Apparatus  for  Placing  Lenses  in  Front  of  the  Patient's 
Eye. — There  are  several  different  forms  in  the  market,  their 
purpose  being  twofold — to  save  time  and  any  extra  move- 
ments on  the  part  of  the  surgeon.  Of  these,  that  of  Wurde- 
mann  {American  Journal  of  Ophthalmology,  p.  223,  1891) 
seems  the  best  hand  skiascope.  A  reference  to  the  sketch 
(Fig.  23)  shows  this  instrument  with  its  convenient  handle 


Fig.  24. — Jennings'  Skiascopic  Disc. 

wherewith  the  patient,  being  instructed,  raises  or  lowers 
the  disc  in  front  of  the  eye,  with  its  smooth  broad  edge 
resting  against  the  side  of  the  nose. 

One  column  contains  plus  and  the  other  minus  lenses, 
and  as  it  is  reversible,  these  may  be  placed  in  front  of  the 
eye,  as  the  surgeon  directs. 

The    most    modern   and  complete  revolving  skiascopic 


MOVEMENT   OF   THE   MIRROR.  35 

disc  is  that  of  Jennings  (Fig.  24)  {American  Journal  of  Oph- 
thalmology, November,  1896,  and  April,  1899),  and  may 
be  best  understood  from  his  own  description:  "It  consists 
of  an  upright  metal  frame,  18  inches  high  and  7  inches 
wide,  placed  at  the  end  of  a  table  26  i  /2  inches  long  and  12 
inches  wide.  In  the  upright  frame  is  an  endless  groove 
containing  39  lenses  and  i  open  cell.  At  the  lower  end  of 
the  frame  is  a  strong  driving  wheel  connected  with  a  hori- 
zontal rod  running  the  length  of  the  table  to  a  handle  with 
which  the  operator  rotates  the  lenses.  Facing  the  operator 
and  close  to  his  hand  is  a  large  disc,  on  which  is  indicated 


Fig.  25. — Author's  Trul-frame  with  Axonometers  Attached. 
{Drawing  reduced  in  size.) 

the  strength  of  the  lens  presenting  at  the  sight-hole.  The 
white  numbers  on  a  black  ground  represent  convex,  and 
the  black  numbers  on  the  white  ground  concave,  lenses. 
The  lenses  range  from  0.25  D.  to  9  D.  plus,  and  from  0.25 
D.  to  9  D.  minus.  The  sight-holes  are  7  /8  of  an  inch  in 
diameter,  and  are  placed  about  five  inches  from  the  top  of 
the  upright  frame.  In  front  of  each  sight-hole  is  a  cell 
marked  in  degrees  to  hold  stronger  spheres  or  cy  inders. 
The  central  portion  of  the  upright  is  cut  away,  leaving  a 
space  for  the  face  of  the  patient.  A  movable  blinder  is 
hung  from  the  top,  while  the  chin-rest  moves  up  and  down 


36  RETINOSCOPY. 

on  two  parallel  rods  and  is  held  in  place  by  a  thumb-screw. 
The  whole  is  mounted  on  a  strong  adjustable  stand,  which 
is  raised  or  lowered  by  means  of  a  rack  and  pinion."  The 
essential  advantages  of  this  skiascope  are  as  follows: 

1.  It  saves  time  and  fatigue  in  changing  lenses. 

2.  It  is  under  the  immediate  control  of  the  operator,  and  indi- 
cates the  lens  in  front  of  the  sight-hole  without  his  getting  up. 

3.  The  mechanism  is  simple,  durable,  and  easy  to  operate. 

4.  The  cornea  is  accurately  centered  and  the  lens  per- 
pendicular to  the  front  of  the  eye  (a  very  important  con- 
sideration, and  one  not  possible 
with  every  kind  of  trial  frame). 

5.  The  instrument  is  of  such 
length  that  the  operator  is 
always  one  meter  distant  from 
the  patient. 

While  either  the  hand  or  the 
revolving  disc  is  recommended, 
yet  the  writer  is  partial  to  an  ac- 
curately fitting  trial  frame  (Fig. 
Fig.    26.-Author's    Trial-         n  -         ^^      ^  ^^^^  the 

CASE    FOR    ReTINOSCOFY.  ^^'  ° 

trail-case,  which  should  be  con- 
veniently at  hand.  The  following  suggestions  in  the 
selection  and  use  of  the  trial-frame  are  offered:  The 
temples  should  rest  easily  on  the  ears,  the  nose-piece  (brdge) 
to  have  a  sufficiently  long  post  to  permit  the  eye-pieces  to  fit 
high  and  accurately  over  any  pair  of  eyes,  especially  those 
of  children,  and  have  the  cornea  occupy  the  center  of  each 
eye-piece.  Correct  results  cannot  be  expected  or  quickly 
obtained  unless  the  neutralizing  lenses  be  placed  with  their 
centers  corresponding  to  corneal  centers,  and  at  the  same 
time  perpendicular  to  the  front  of  the  eye.  A  convenient 
and  small  trial-case  containing  a  row  of  plus  and  minus 
spheres,  from  0.12  to  10  D.,  is  shown  in  Figure  26. 


>^ 


CHAPTER  V. 

RETINOSCOPY     IN     EMMETROPIA     AND     THE     VARIOUS 
FORMS  OF  REGULAR  AMETROPIA.— AXONOMETER. 

Hyperopia. — In  this  variety  of  refraction  the  direction 
of  the  movement  of  the  retinal  illumination  is  with  the 
movement  of  the  light  on  the  patient's  face.  By  reflecting 
the  light  through  the  various  meridians  and  observing  the 
rate  of  movement,  a  strong  or  weak  plus  sphere,  according  to 


\ 


Fig.  27.  Fig.  28. 

Fig.  27. — Gray  Reflex  as  seen  in  High  H^  perdpia,  even  Darker  than 

THE  Picture  shows  It. 

Fig.  28. — Gray  Reflex,  with  Crescent  Edge  by  tilting  Mirror  to 

Left,  Darkness  or  Shadow  Following. 

the  apparent  rate  of  movement,  is  placed  before  the  eye, 
and  the  rate  of  movement  of  the  retinal  illumination  is 
again  noted. 

Practice  alone  will  guide  the  observer  in  a  quick  appre- 
ciation of  the  approximate  strength  of  neutralizing  lens  to 
thus  employ. 

If  the  movement  of  the  illumination  appears  slow,  and 
the  observer  places  a  +  2.75  D.  before  the  eye  for  its  neutral- 
ization, and  the  illumination  then  becomes  brilliant  and 
appears  to  move  fast  and  with  the  light  on  the  face,  the 
hyperopia  is  still  sHghtly  uncorrected  and  a  stonger  lens 
must  be  substituted.     (At  this  point  in  the  examination  the 

37 


S^  RETINOSCOPY. 

five-millimeter  opening  in  the  light-screen  may  be  used  to 
advantage.) 

Removing  the  +2.75  D.  and  substituting  a +3.25  D., 
if  the  retinal  illumination  is  then  found  to  move  opposite  to 
the  movement  of  the  light  on  the  face,  the  refraction  of  the 
eye  will  then  be  represented  by  the  lens  numbered  between 
the  -\-  2.75  D.  and  the  3.25  D.,  which  is  3  D.  (See  example, 
p.  28,  Chap.  IV).  Now,  while  the  +3  D.  has  brought  the 
emergent  rays  to  a  focus  at  one  meter,  it  has  made  the  eye 
myopic  just  one  diopter,  so  that  in  taking  the  patient  from 
the  dark  room  to  test  his  vision  at  six  meters,  or  infinity, 
this  one  diopter  (artificial  myopia)  must  be  subtracted  from 


Fig  29. 

the  +3  D.,  which  would  leave  +2  D.,  the  amount  of  the 
hyperopia. 

^    A  reference  to  Figure  30  will  illustrate  the  description 
just  given. 

Figure  29  is  the  hyperopic  eye  under  examination,  and 
shows  the  mirror  at  one  meter's  distance,  with  the  light 
five  inches  from  the  mirror.  The  dotted  lines  represent 
the  rays  proceeding  divergently  from  the  eye  under  exami- 
nation; the  dark  lines  show  the  reflected  rays  from  the 
mirror,  which  illuminate  the  retina  and  have  an  imaginary 
focus  (dotted  lines)  beyond  the  retina. 

Figure  30  is  a  profile  view  showing  the  hyperopic  eye 
with  neutralizing  lens  in  position.  The  dotted  lines  with 
arrow-heads  indicate  the  direction  the  rays  would  naturally 


EMMETROPIA.  39 

take  coming  from  the  eye.  The  lens  (  +  3  D.)  in  front  of 
the  eye  is  just  sufficiently  strong  to  bend  these  divergent 
rays  and  bring  them  to  a  focus  at  one  meter's  distance 
(artificial  point  of  reversal).  In  other  words,  +2  D.  of  the 
three  diopters  thus  placed  before  this  hyperopic  eye  would 
have  bent  the  divergent  rays  and  made  them  parallel, 
or  emmetropic,  but  the  additional  one  diopter  bends  the 
rays  still  more  and  brings  them  to  a  focus  (P.  R.,  point  of 
reversal)  at  one  meter. ,  If,  now,  with  the  +  3  D.  before  the 
eye,  the  observer  approaches  the  eye  thus  refracted  and 
observes  the  retinal  illumination  closer  than  one  meter,  he 
will  be  inside  of  the  point  of  reversal,  and  consequently 


see  an  erect  image  moving  rapidly  with  the  direction  of  the 
movement  of  the  mirror.  If  beyond  this  point  of  reversal 
(P.  R.),  he  would  get  an  inverted  image  and  the  retinal 
illumination  moving  rapidly  in  a  direction  opposite  to  the 
movement  of  the  mirror. 

Emmetropia. — The  emergent  rays  from  an  emme- 
tropic eye  are  always  parallel,  and  the  observer  seated 
at  one  meter  sees  the  pupillary  area  in  such  an  eye  brilliantly 
illuminated,  the  illumination  moving  rapidly  with  the  light 
on  the  face  as  the  mirror  is  slowly  tilted. 

A  reference  to  Figure  31  shows  the  emmetropic  eye 
under  examination  with  the  position  of  light,  mirror,  and 
eye,  as  in  Figure  29.  The  dotted  lines  indicate  the  parallel 
emergent  rays,  and  the  soHd  lines  the  divergent  rays  from 


40  RETINOSCOPY. 

the  mirror  with  an  imaginary  focus  just  beyond  the  retina. 
The  purpose  is  this  instance,  as  in  all  others  of  retinoscopy, 
is  to  place  such  a  neutralizing  lens  before  the  eye  as  will 
bend  the  emergent  rays  and  bring  them  to  a  focus  at  a 
certain  definite  distance,  making  the  emergent  rays  from 
a  point  on  the  retina  come  to  a  focus  on  the  observer's 
retina.  Therefore,  to  change  this  illumination  so  that  no 
movement  can  be  seen  to  take  place  in  the  pupillary  area, 
and  at  the  same  time  have  the  emergent  rays  focus  on  the 
observer's  retina,  a  + 1  sphere  must  be  placed  before  the 
eye. 

Just  here  the  writer  wishes  to  impress  upon  the  beginner 


Fig.  31. 

the  great  importance,  as  mentioned  on  page  41,  of  refract- 
ing the  macular  region.  To  accomplish  this,  the  patient 
must  fix  his  gaze  upon  the  metal  disc  or  letters  on  the  disc  of 
the  mirror.  As  the  region  of  the  macula  is  departed  from, 
the  strength  of  the  neutralizing  lens  grows  slightly  stronger 
in  emmetropia  and  hyperopia,  and  diminishes  in  myopia. 
A  reference  to  Figure  ^2  will  give  an  idea  of  what  is  meant, 
and  show  that  radii  drawn  from  the  nodal  point  are  all 
shorter  than  the  one  to  the  fovea. 

-  Myopia. — In  myopia  the  emergent  rays  always  converge 
to  the  far-point  (point  of  reversal),  and  the  observer,  seated 
at  one  meter  distant  from  the  eye,  will  have  the  apparent 
movement  of  the  retinal  illumination  going  opposite  to 


MYOPIA.  41 

the  light  on  the  face  if  the  myopia  exceeds  one  diopter, 
and  with  the  light  on  the  face  if  the  myopia  is  less  than  one 
diopter.  If  the  myopia  should  be  just  one  diopter,  then 
the  emergent  rays  would  focus  on  the  observer's  retina  at 
one  meter,  and  there  will  not  be  any  neutralizing  lens  required 
to  accomplish  this  purpose;  but  if  the  emergent  rays  focus 
beyond  one  meter,  the  observer  will  be  within  this  point 
of  reversal  or  focus,  and  will,  therefore,  have  an  erect  image, 
moving  fast  with  the  movement  of  the  mirror,  and  will  have 
to  place  before  the  eye  a  plus  lens  of  less  than  one  diopter  to 
bring  the  point  of  reversal  up  to  the  distance  of  one  meter. 
When  the  myopia  is  more  than  one  diopter,  and  observer 
at  one  meter,  the  emergent  rays  will  have  focused  somewhere 
between  the  observer  and  the  patient,  and,  as  a  result,  the 
retinal  illumination  appears  to  move  oppo- 
site to  the  Hght  upon  the  face;  more  or 
less  rapidly,  according  to  the  amount  of 
myopia;  and  a  concave  or  minus  lens 
must  be  placed  in  front  of  such  an  eye 
that  will  bring  the  emergent  rays  to  a 
focus  at  one  meter,  or,  in  other  words, 
will   stop  all  apparent  movement  of  the  Fig.  32. 

retinal  illumination.     If,   for  example,  a 

—  2.75  D.  has  been  so  placed,  and  the  movement  is  still 
sHghtly  opposite  to  the  movement  of  the  mirror,  and  a 

—  3.25  D.  substituted  makes  the  retinal  illumination  move 
with  the  movement  of  the  mirror,  then  the  neutrahzing  lens 
for  one  meter  will  be  numbered  between  —2.75  D.  and 

—  3.25  D.,  which  will  be  —3  D. 

Figure  2>3  shows  the  myopic  eye  just  described,  with 
the  position  of  the  mirror,  light,  and  eye  as  in  Figures  29 
and  31.  The  solid  lines  represent  the  rays  reflected  diver- 
gently from  the  mirror  focusing  at  a  point  in  the  vitreous 
before  coming  to  the  retina,  and  the  broken  lines  show 


42 


RETINOSCOPY. 


the  rays  emerging  from  a  point  on  the  retina  and  then 
converging  to  the  focus,  far-point,  or  point  of  reversal 
close  to  the  eye,  between  the  eye  and  the  mirror.  The 
observer,  seated  with  the  mirror  one  meter  distant,  gets  an 
opposite  movement  in  the  pupillary  area  from  the  direction 
in  which  he  moves  his  mirror,  and,  of  course,  an  inverted 
image.  If  the  observer  had  his  eye  at  the  point  where  the 
emergent  rays  focused  (dotted  lines  cross),  he  would  not 
recognize  any  movement  in  the  pupillary  area,  and  it 
would  have  a  uniform  reflex.  The  amount  of  the  myopia 
is  equal  to  the  distance  measured  from  this  point  of  reversal 
to  the  cornea;  for  example,  if  the  distance  (point  of  reversal) 


Fig.  S3. 

was  twenty-five  cm.  from  the  patient's  eye,  then  the  amount 
of  the  myopia  would  be  four  diopters;  if  at  ^^  cm.,  then  3 
D.,  etc. 

Figure  34  is  a  profile  view  of  the  myopic  eye.  The 
dotted  lines  show  the  rays  coming  from  a  point  on  the 
retina  and  focusing  at  the  far-point  (f.p.);  the  solid  lines 
show  the  emergent  rays  acted  upon  or  bent  by  a  plano- 
concave lens  of  three  diopters,  which  has  lessened  the 
convergence  of  these  emergent  rays  and  put  the  far-point 
farther  from  the  eye,  or  at  a  distance  of  one  meter.  The 
observer  at  this  distance  does  not  appreciate  any  movement 
in  the  pupillary  area,  but  if  he  moves  the  light  and  mirror 
closer  to  the  eye  he  is  then  inside  the  point  of  reversal 


RULES.  43 

and  gets  an  erect  image  moving  with  the  movement  of  the 
mirror;  if  beyond  the  one  meter's  distance,  an  inverted 
image  and  movement  against  the  movement  of  the  mirror 
will  be  seen.  If  a  -4  D.  lens  had  been  placed  before  this 
myopic  eye,  the  emergent  rays  would  have  proceeded  from 
it  parallel,  and  the  observer,  at  one  meter,  would  have 
the  same  conditions  as  in  the  refraction  of  an  emmetropic 
eye.  Figure  31;  but  as  only  a  -3  D.  glass  was  used,  the' 
eye  has  one  diopter  of  its  myopia  uncorrected.  From 
the  description  of  retinoscopy  in  hyperopia,  emmetropia, 
and  myopia,  just  given,  the  student  will  recognize  at  once 
that  the  hyperopic,  emmetropic,  and  myopic  eyes  of  less 


/   METER 


Fig.  34. 

than  one  diopter,  working  with  the  plane  mirror  at  one 
meter's  distance,  are  given  a  stronger  refraction  than  they 
naturally  call  for,  or,  in  other  words,  are  made,  artificially, 
myopic  one  diopter.  And  the  myopic  eye  of  more  than 
one  diopter,  under  similar  conditions,  being  already  myopic, 
retains  one  diopter  of  its  myopia.  To  give  a  patient  thus 
refracted  with  the  retinoscope  his  emmetropic  correction 
(correction  for  parallel  rays  of  light),  an  allowance  must 
always  he  made,  in  all  meridians,  of  one  diopter,  no  matter 
what  the  refraction.  The  artificial  myopia  thus  produced 
at  one  meter  gives  the  following  rules  for  glasses  required 
for  infinity : 

Rules. — I.  When  the  neutralizing  lens  employed  is  plus, 
then  subtract  one  diopter. 


r 


44  RETINOSCOPY. 

2.  When  the  neutraHzing  lens  employed  is  minus,  then 
add  a  -I  D.,  or  what  is  more  simple,  or  even  a  better  rule, 
is,  to  always  add  a  -i  sphere  to  the  neutralizing  lens  ob- 
tained in  the  dark  room  when  working  at  one  meter,  and  the 
result  will  be  the  emmetropic  or  infinity  correction. 

Examples : 

.Dark  Room, +0.50    0.00+ 1.00+2.00— i. 00 

Adding, —  i.oo— i.oo— i.oo— i.oo— i.oo 

Emmetropic  Correction,   .    .    .   —0.50— i.oo— 0.00+ i.oo— 2.00 

The  main  point  in  all  retinoscopic  work  to  remember  in 
changing  from  the  dark  room  to  the  six-meter  correction, 
is  to  always  allow  for  the  distance  from  the  patienfs  eye  to 
the  point  of  reversal — i.e.,  if  working  at  half  a  meter,  allow 
two  diopters;  if  at  two  meters,  0.50  D.,  if  at  four  meters, 
0.25  D.,  etc. 

"Regular  Astigmatism.— When  refracting  with  the  ret- 
inoscope,  the  observer  should  remember  that  he  is  refract- 
ing the  meridian  in  the  direction  of  which  he  moves  the  mirror. 
Particular  attention  is  called  to  this  important  fact  on 
account  of  the  confusion  sometimes  arising  in  the  student's 
mind  from  the  use  of  the  ophthalmoscope,  where  the  re- 
fractive condition  of  a  certain  meridian  is  estimated  by 
the  strength  of  the  lens  used  to  see  clearly  the  vessels 
at  right  angles  to  it.  Astigmatism  being  present  in  an  eye, 
means  a  difference  in  the  strength  of  the  glass  required 
for  the  two  principal  meridians,  which,  with  few  exceptions, 
are  at  right  angles  to  each  other,  and  it  is  to  these  two 
principal  meridians  only  that  the  observer  pays  attention; 
for  example,   the  eye  that  takes  the   following  formula, 

+  i.ooD.O-fi.oo  c.  axis  105°, 
means  that  in  the  105  meridian  there  is  +1  D.  and  in  the 
15  meridian  a  +2  D.     In  the  dark  room  a  +2  sphere  in 
front  of  such  an  eye  at  one  meter  would  correct  the  105 


REGULAR    ASTIGMATISM.  45 

meridian  and  partly  correct  the  15  meridian;  or  a  +3  D. 
would  correct  the  15  and  over-correct  (movement  against) 
the  105  meridian.  When  with  +  2  D.  the  105  meridian  is 
corrected  and  the  15  only  partly  so,  there  is  seen  in  the  15 
meridian  a  band  of  Hght  which  stands  or  extends  across 
the  pupil  in  the  105  meridan  and  moves  across  the  pupi 


+3.0 


from  left  to  right  with  the  movement  of  the  mirror  as  the 
light  is  reflected  through  the  15  meridian. 

The  presence  of  this  band  of  light  after  the  meridian 
of  least  ametropia  has  been  corrected  always  signifies  as- 
tigmatism, and  the  axis  it  subtends — in  this  case  105° 
gives  the  axis  of  the  cylinder  in  the  prescription;  and  the 
amount  of  the  astigmatism,  or  the  strength  of  the  cylinder 
required,  is  the  difference  between  the  strength  of  the  two 
spheres  employed.  Figure  35  shows  the  method  of  writing 
such  a  dark  room  correction,  and  adding,  according  to  our 
rule,  a  -i  to  this  dark  room  work,  we  get  our  original  formula : 

-l-i .  00  D.  O -|- 1 .  00  c.  axis  105°. 
The  method  of  correcting  with  spheres  (Fig.  26)  will  be 
found  much  more  satisfactory  than  by  placing  a  +2  D.,  as 
called  for  in  the  105  meridian,  then  adding  and  changing 
cylinders  until  the  correct  one  is  found.  It  takes  much 
time  and  care  to  get  the  cylinder  axis  just  right,  and  is 
most  difiicult  in  the  dark  room.     After  the  result  has  been 


46  RETINOSCOPY. 

obtained  with  spheres,  the  observer  may,  if  he  is  so  disposed, 
prove  it  before  leaving  the  dark  room  with  the  sphero- 
cylinder  combination. 

Astigmatism  may  or  may  not  be  recognized  on  first 
inspection  of  the  fundus-refiex,  this  depending  entirely 
on  the  refraction;  if  it  be  a  high  astigmatism  with  a  small 


Fig.  36.  Fig.  37. 

Fig.  36, — Band  of  Light  at  Axis  60°,  with  the  60°  Meridian  Neutral- 
ized. No  movement  of  the  illumination  can  be  recognized  in  the  60° 
meridian. 

Fig.  37. — Shows  the  same  as  Figure  36,  but  the  band  of  light  with  straight 
edge  has  been  moved  upward  and  to  the  left  by  tilting  the  mirror  in  the 
150°  meridian. 

amount  of  refractive  error  in  the  opposite  meridian,  as  in 
one  of  the  following  formulas, 

+  1.00  D.  O +3.00  c.  axis    45°, 

—  1. 00  D.  O -4.00  c.  axis  180°, 

then  the  band  of  light  so  characteristic  of  astigmatism 
will  be  plainly  seen  on  first  inspection,  extending  across 
thie  pupil  before  any  neutralizing  lens  has  been  placed  in 
position;  but  if  the  hyperopia  or  myopia  be  high  and  the 
cylinder  required  is  low,  as  in  one  of  the  following  formulas, 

-f3.ooD.O+o.75c.  axis  105°, 

—  4. 00  D.  O  —  1 .  00  c.  axis  165°, 

then  the  bajnd  of  light  is  not  recognized  on  first  inspection 
or  until  an  approximate  correction  has  been  placed  before 
the  eye.  To  get  an  idea  of  what  the  band  of  light  looks 
like,  the  beginner  may  refer  to  Figures  7,6  and  38;  or  focus 
rays  of  light  through  a  strong  cylinder;  or  place  a  +  or—  2  D. 
cylinder  in  front  of  the  schematic  eye  registered  at  zero 
and  study  the  retinal  illumination.     The  student  should 


MIXED    ASTIGMATISM.  47 

bear  in  mind  that  the  axis  of  the  band  of  light  appears  on 
the  meridian  of  least  ametropia,  and  is  brightest  when  this 
meridian  has  received  its  full  spheric  correction — the  oppo- 
site meridian  being  only  partly  corrected. 

The  reason  for  the  brightness  of  the  band  of  light  when 
the  meridian  of  its  axis  is  corrected  is  that  any  point  on 
the  retina  in  this  meridian  is  conjugate  to  the  focus  on  the 
observer's  retina  (point  of  reversal),  and  any  movement 
of  the  mirror  in  this  meridian  is  not  recognized,  but  has  a 
uniform  color  and  occupies  the  entire  meridian  of  the  pupil. 
To  recognize  so  small  an  error  as  a  quarterdiopter  cylinder 
— which  is  not  easily  detected,  and 
the  observer,  if  he  is  in  a  hurry, 
might  think  the  case  one  of  simple 
hyperopia  or  myopia — the  writer 
would  suggest  that  when  the  sup- 
posed point  of  reversal  is  reached 
the  correcting  sphere  be  increased 
a  quarter  of  a  diopter,  and  ./  only  ^I'^^-^Z''^,,  p^ 
one  meridian  is  found  over-cor- 
rected (movement  opposite) ,  the  other  remaining  correct  (no 
movement  recognized),  he  then  knows  that  a  quarter  cylin- 
der is  required;  for  example,  a  +  2  D.  is  supposed  to  correct 
all  meridians,  and  yet  by  substituting  a  -f-  2.25  D.,  the  vertical 
meridian  moves  against  and  the  horizontal  remains  station- 
ary; then  a  -fo.25  D.  cylinder  is  called  for  at  axis  90°. 

Cases  having  a  low  astigmatic  error  of  0.50  D.  can  be 
recognized  when  near  the  point  of  reversal  by  the  faint 
shaded  area  on  each  side  of  the  band  of  light,  as  shown  in 
Figure  39 — a  condition  often  overlooked. 

Mixed  Astigmatism.— In  this  condition  of  refraction, 
where  one  meridian  is  myopic  and  the  meridian  at  right 
angles  to  it  is  hyperopic,  the  movement  of  the  retinal 
illumination  in  the  myopic  meridian  will  be  controlled  by 


48  RETINOSCOPy. 

the  amount  of  the  myopia.  The  illumination  in  the  myopic 
meridian,  if  the  myopia  is  less  than  one  diopter,  moves 
with  the  mirror,  and  against  the  movement  of  the  mirror 
if  it  is  more  than  one  diopter;  in  either  instance  the  observer 
gets  a  distinct  band  of  light  in  the  meridians  alternately 
as  each  meridian  is  neutralized  separately  with  a  sphere. 
Taking  the  following  example  (no  glass  in  front  of  the  eye) , 

—  2.00  c.  axis  i8o°0  +1.00  c.  axis  90°, 
the  90  meridian  shows  an  opposite  movement  up  and  down, 
and  in  the  horizontal  the  movement  is  with  the  movement 


Fig.  39. — Band  of  Light  Showing  Half  a  Diopter  of  Astigmatism. 

of  the  mirror.  If,  now,  a  —  i  D.  sphere  be  placed  before  the 
eye,  the  90  meridian  is  neutralized  for  one  meter  distance,  and 
a  bright  band  of  light  is  seen  at  90°,  moving  with  the  move- 
ment of  the  mirror  in  the  horizontal  meridian.  Removing 
the  —  I  D.  and  placing  a  +  2  D.  before  the  eye,  which  would 
neutralize  the  horizontal  meridian  for  one  meter,  a  bright 
band  will  be  seen  in  the  horizontal  meridian  and  moving 
opposite  to  the  movement  of  the  mirror  in  the  90°  meridian. 
Carrying  out  the  rule  of  always  adding  a  —  i  D.  sphere  to 
the  correction  obtained  in  the  dark  room  at  one  meter,  we 
have  —  I  added  to  the  —  i  in  the  vertical  meridian,  making 
—  2D.  axis  180°;  and  adding  —i  to  the  +2  D.  in  the 
horizontal,  we  have  + 1  D.  axis  90°,  or  our  original  formula. 
—  2 .  00  axis  180°  O  + 1 .  00  c.  axis  90°. 
The  rule  for  neutralizing  lenses  in  mixed  astigmatism 
is  the  same  as  for  any  other  form  of  refraction;  namely, 
using  a  plus  lens  when  the  movement  is  with,  and  a  minus 


AXONOMETER.  49 

lens  when  the  movement  is  opposite  to,  the  movement  of 
the  light  on  the  face. 

To  transpose  crossed  cylinders  into  a  sphero-cylinder 
combination  the  writer  would  advise  using  the  rule  of  Dr. 
Harry  S.  Pearse,  of  Albany,  which  is  as  follows: 

"  The  cylinder  is  the  sum  of  the  two  cylinders  with  the 
sign  and  axis  of  one  of  the  cylinders^     The  sphere  is  the 
strength  of  the  other  cylinder  with  its  sign."     In  the  above 
formula,  the  sphero-cylinder  combination  will  be 
—  2  D.  O  +  3 .  00  c.  axis  90°. 

Axonometer. — To  find  the  exact  axis  subtended  by  the 
band  of  light  while  studying  the  retinal  illumination,  when 


Fig.  40. 

the  meridian  of  least  ametropia  has  been  corrected,  the 
writer  has  suggested  a  small  instrument,  which,  for  want 
of  a  better  name,  he  has  called  an  axonometer. 

Figure  40  shows  this  instrument,  and  Figure  41  the  axon- 
ometer in  position. 

The  original  description  of  this  device  was  published 
in  The  Medical  News,  March  3,  1894,  as  follows:  "The 
direction  of  the  principal  meridians  of  corneal  curvature 
is  often  difficult  to  determine,  and  the  statement  of  the 
patient  must  be  accepted  when  confirming  the  shadow- 
test  correction;  or,  if  there  is  still  uncertainty,  the  ophthal- 
4 


so 


RETINOSCOPY. 


mometer  of  Javal  may  be  of  service.  The  axonometer 
is  a  black  metal  disc,  with  a  milled  edge,  one  and  one-half 
mm.  in  thickness,  of  the  diameter  of  the  ordinary  trial- 


tlG.  41. 

lens,  and  mounted  in  a  cell  of  the  trial-set.  It  has  a  central 
round  opening  12  mm.  in  diameter — the  diameter  of  the 
average  cornea  at  its  base.  Two  heavy  white  lines,  one  on 
each  side,  pass  from  the  circumference  across  to  the  central 


Fig.  42. 

opening,  bisecting  the  disc.  To  use  the  axonometer,  place 
it  in  the  front  opening  of  the  trial-frame,  and  with  the 
patient  seated  erect  and  frame  accurately  adjusted  so  that 


AXONOMETER. 


51 


the  cornea  of  the  eye  to  be  refracted  occupies  the  central 
opening,  proceed  as  in  the  usual  method  of  making  the 
shadow  test.  As  soon  as  that  lens  is  found  which  corrects 
the  meridian  of  least  ametropia,  and  the  band  of  light 
appears  distinct,  turn  the  axonometer  slowly  until  the  two 
heavy  white  lines  accurately  coincide,  or  appear  to  make 


Fig.    43. — Trial-frame    with   Axonometers   in   Position    Indicating 
Symmetric  Astigmatism. 


one  continuous  line  with  the  band  of  light  (see  Fig.  41). 

"The  degree  marks  on  the  trial-frame  to  which  the 
arrow-head  at  the  end  of  the  white  lines  then  points  is  the 
exact  axis  for  the  cylinder.  The  axonometer  possesses  the 
following  points  of  merit: 

'^  Simplicity. 

''Accuracy. 


52 


RETINOSCOPY. 


"Small  expense. 

"It  covers  an  unnecessary  part  of  the  trial-lens  which 
too  frequently  gives  annoying  reflexes  and  images. 

"It  saves  time,  avoids  the  statement  of  the  patient,  and 
renders  the  ophthalmometer  unnecessary. 

"Its  color  (black)  absorbs  the  superfluous  light  rays 
from  the  mirror  and  gives  a  stronger  contrast  to  the  reflex 
and  central  illumination. 


Fig.   44. — Trial-frame  with  Axoxometers    in    Position   Indicating 
Asymmetric  Astigmatism. 

"Limiting  the  field  of  vision  in  children,  it  permits  of 
more  concentrated  attention. 

"For  children  and  nervous  patients,  when  it  is  difficult 
to  use  the  ophthalmometer,  his  simple  appliance  is  of 
great  service." 


AXONOMETER.  53 

Lately  the  writer  has  improved  the  axonometer  by  having 
the  white  lines  broadened  to  four  millimeters,  which  is  a 
decided  advantage  over  the  instrument  shown  in  Figures 
40  and  41  as  the  broad  line  is  easily  seen  at  one  meter 
distance.  This  axonometer,  shown  in  Figure  42,  is  made 
of  thick  celluloid. 

Figure  43  shows  the  trial  frame  with  axonometers  in 
position  indicating  symmetric  astigmatism. 

Figure  44  shows  the  trail  frame  with  axonometers  in 
position  indicating  asymmetric  astigmatism. 


CHAPTER  VI. 

RETINOSCOPY  IN  THE  VARIOUS  FORMS  OF  IRREGULAR 
AMETROPIA.— RETINOSCOPY  WITHOUT  A  CYCLOPLE- 
GIC— THE  CONCAVE  MIRROR.— DESCRIPTION  OF  THE 
AUTHOR'S  SCHEMATIC  EYE  AND  LIGHT-SCREEN.— 
LENSES  FOR  THE  STUDY  OF  THE  SCISSOR  MOVEMENT, 
CONIC  CORNEA,  AND  SPHERIC  ABERRATION. 

Irregular  Astigmatism. — This  condition  is  either  in 
the  cornea  or  in  the  lens,  or  in  both  structures  in  one  and 
the  same  eye;  in  any  instance  it  is  confusing  to  the  beginner, 
and  even  the  expert  must  work  slowly  to  obtain  a  definite 
result.  The  corneal  form  is  most  diflScult  to  refract  as 
the  retinal  illumination  is  more  or  less  obscured  by  areas 
of  darkness.  The  illumination  between  these  dark  areas 
appears  to  move  with,  in  places,  and  in  others  against,  the 
movement  of  the  mirror.  By  moving  the  mirror  so  as  to 
make  the  light  describe  a  circle  around  the  pupillary  edge, 
a  most  unique  kaleidoscopic  picture  is  obtained,  which  is 
quite  diagnostic  of  the  condition.  To  refract  an  eye  with 
this  irregularity  the  observer  may  have  to  change  his  posi- 
tion several  times,  going  closer  to  or  farther  away  from 
the  patient.  Very  often  these  eyes  are  astigmatic,  and 
the  band  of  light  may  be  promptly  noted  by  the  observer 
changing  his  position  as  suggested,  and  at  the  same  time 
placing  a  neutralizing  lens  before  the  eye.  Care  must  be 
taken,  also,  to  refract  in  the  area  of  the  cornea  that  will 
correspond  to  the  small  pupil  when  the  effect  of  the  cyclo- 
plegic  passes  away.  It  is  often  best,  in  these  cases  of 
irregular  corneal  astigmatism,  to  make  a  record  of  the  cor- 
rection found  and  use  it  as  a  guide  in  a  post-cycloplegir 
manifest  refraction. 

54 


SCISSOR   MOVEMENT.  55 

Irregular  astigmatism  of  the  lens  is  frequently  more 
or  less  uniform,  and  not  so  broken  as  in  the  corneal  variety. 
Figures  45  and  46  show  two  kinds  of  irregular  lenticular 
astigmatism. 

Figure  45  illustrates  the  spicules  pointing  in  from  the 
periphery,  and  so  long  as  these  do  not  encroach  upon  the 
pupillary  area,  they  do  not  usually  in  themselves  interfere 
with  vision;  they  are  not  often  recognized  until  the  pupil 
is  dilated,  are  then  very  faint,  and  not  usually  made  out 
until  the  point  of  reversal  is  approached.  Figure  46  is 
another  form  of  irregular  astigmatism,  and  a  very  inter- 


FiG.  45.  Fig.  46. 

Irregular  Lenticular  Astigmatism. 

esting  picture  as  studied  with  the  retinoscope;  and,  as  in 
Figure  45,  when  very  faint,  is  not  made  out  until  close  to 
the  point  of  reversal.  These  two  forms  of  irregular  lenticu- 
lar astigmatism,  when  just  beginning,  are  very  seldom  seen 
with  the  ophthalmoscope;  the  stria tions  are  too  fine  to  be 
made  out  except  under  the  conditions  just  described, 
and  when  recognized  are  of  inestimable  value  from  a  point 
of  prophylactic  treatment,  calling  for  a  change  of  occupa- 
tion, rest  to  the  eyes,  and  carefully  selected  glasses,  the 
latter  often  being  weak  lenses.  These  lenticular  conditions 
not  infrequently  accompany  the  "flannel-red"  fundus, 
the  "fluffy  eye  ground,"  the  "shot-silk  retina,"  the  "woolly 
choroid,"  etc. 

Scissor  Movement. — Another  form  of  astigmatism  that 
may  be  classed  as  irregular  is  where  there  are  two  areas 
of  light,  each  with  a  straight  edge,  and  usually  seen  ctn 


56  RETINOSCOPY. 

the  horizontal  meridian,  or  inclined  a  few  degrees  from  the 
horizontal,  and  moving  toward  each  other  as  the  mirror 
is  tilted  in  the  opposite  meridian;  in  other  words  as  the 
observer  is  seated  at  one  meter  he  sees  an  area  of  light 
above  and  an  area  of  light  below  with  a  dark  interspace 
(Fig.  48).     As  the  mirror  is  slowly  tilted  in  the  vertical 


Fig.  47. — Light  Areas  Coming  Together  and  Dark  Interspace 
Fading. 

meridian  these  light  areas  approach  and  are  followed 
by  darkness  or  shadow,  and  at  the  same  time  the  dark 
interspace  begins  to  fade,  giving  the  picture  as  shown  in 
Figure  47.  When  the  light  areas  are  brought  together, 
they  result  in  a  horizontal  band  of  light,  as  seen  in  Figure 
49,  and  at  this  point  resemble  the  ordinary  band  of  light 
as  seen  in  regular  astigmatism.  This  movement  of  the 
light  areas  is  likened  to  the  opening  and  closing  of  the 
scissor  blades,  and  hence  the  name  of  scissor  movement. 

These  cases  are  more  or  less  difficult  to  refract,  but  the 
presence  of  the  two  areas  of  light  with  the  dark  interspace 
will  often  assist  in  a  correct  selection  of  glasses,  for  while 
they  are  generally  of  the  compound  hyperopic  variety, 
calling  for  a  plus  sphere  and  plus  cylinder,  yet  practice 
and  the  patient's  statement  often  call  for  a  plus  sphere 
and  minus  cylinder. 

With  the  following  formula, 

+  2.00  D. 0  +  0. 75  c.  axis  90°, 
substituting  a  sphere  the  strength  of  the  combined  values 


SCISSOR    MOVEMENT.  57 

of  the  sphere  and  cylinder,  and  using  a  minus  cylinder  of 
the  same  number  as  the  plus  cylinder  at  the  opposite  axis, 
the  result  will  be, 

+  2.75  D.  O  —0.75  c.  axis  180°. 
The  vision  with  the  latter  formula  is  much  better  in 
many  instances  than  with  the  former,  and  though  either 
formula  would  be  correct,  yet  the  latter  is  practically  the 
better  of  the  two,  and  should  be  ordered  when  so  found. 
The  writer's  method  of  procedure  when  he  recognizes  the 
scissor  movement  is  to  tilt  the  mirror  until  the  two  light 


©/■k 
^^^^J 


Fig.  48.  Fig.  49. 

Fig.  48. — Light  Area  Above  and  Below,  with  Dark  Interspace. 
Fig.  49. — Light  Areas  Brought  Together. 

areas  are  brought  into  one  band  of  light  as  shown  in  Fig. 
49  and  then  to  reflect  the  light  through  the  meridian  of 
this  band  (in  this  instance  as  illustrated,  the  180  meridian). 
Having  obtained  the  lens  which  neutralizes  the  movement 
in  this  meridian,  the  writer  does  not  attempt  to  find  the 
neutralizing  lens  for  the  opposite  meridian  but  goes  from 
the  dark  room  to  the  trial-case  and  places  before  the  pa- 
tient's eye  that  sphere  which  corrects  the  refraction  in  the 
horizontal  meridian.  For  instance,  if  +3.75  D.  corrects 
the  horizontal  meridian  at  one  meter,  then  +2.75  D.  sphere 
is  placed  before  the  eye,  and  a  minus  cylinder  (beginning 
with  —0.50  at  axis  180  degrees)  is  placed  in  front  of  the 
sphere  and  the  strength  of  this  minus  cylinder  is  gradually 
increased  so  long  as  the  visual  acuity  improves.  In  other 
words  the  writer  does  not  attempt  to  estimate  the  refraction 
with  the  retinoscope  in  the  meridian  opposite  to  the  bands 


58  RETINOSCOPy. 

of  light.  The  condition  which  may  be  the  probable  cause 
of  the  scissor  movement  is  a  slight  tilting  of  the  lens  (see 
Fig.  50) — that  is,  the  antero-posterior  axis  of  the  lens  is 
not  at  right  angles  to  the  plane  of  the  cornea,  thus  making 
one  portion  of  the  pupil  myopic  (area  of  light  moving  op- 
posite) and  the  other  portion  hyperopic  (area  of  light  moving 
with  the  movement  of  the  mirror) .  This  condition  may  be 
simulated  by  placing  a  convex  lens  at  an  angle  before  the 
schematic  eye,  or  reflecting  the  light  into  the  eye  obliquely, 
or  by  using  the  combination  lens  in  front  of  the  schematic 
eye,  as  suggested  on  page  66. 
What  causes  the  tilting  of  the  lens  the  writer  is  not  prepared 


Fig.  50. 

to  state  positively;  it  may  be  congenital,  and  yet  careful 
inquiry  of  the  patients,  in  many  instances,  has  shown  that 
it  is  most  likely  due  to  using  the  eyes  to  excess  in  the  recum- 
bent posture.  It  may  be  a  coincidence,  but  most  of  the 
cases  of  scissor  movement  seen  by  the  author  have  been 
in  adults,  and  those  who  were  in  the  habit  of  reading 
while  lying  down,  reading  themselves  to  sleep  at  night  in 
bed.^  Other  cases  were  seen  among  paper-hangers, 
whose  occupation  compelled  them  to  look  upward  much 
of  the  time.  These  do  not  seem  unlikely  causes,  especially 
when  the  anatomy  of  the  ciliary  region  is  considered,  the 
strain  of  the  accommodation  (possibly  spasm)  during  the 

'  The  writer  does  not  wish  to  be  misunderstood  and  does  not  say  that 
every  one  who  uses  his  eyes  in  this  faulty  position  must  develop  this  form  of 
irregular  astigmatism. 


COMPOUND    IRREGULAR   ASTIGMATISM.  59 

faulty  position  of  the  eye  tilting  the  lens  as  it  rests  upon  the 
vitreous  body.  This  form  of  astigmatism,  so  far  as  known, 
remains  a  permanent  one  even  after  a  cessation  from  the 
original  cause  and  correcting  glasses  have  been  ordered. 
The  retinoscope  is  the  only  instrument  of  precision  we  have 
in  diagnosing  this  condition.  The  ophthalmoscope  may 
recognize  the  presence  of  the  astigmatism,  but  not  its 
character,  and  the  ophthalmometer  only  records  the  corneal 
curvature.  Cases  of  aphakia  (following  cataract  extraction) 
frequently  show  the  scissor  movement  during  the  process 
of  retinoscopy.  This  is  undoubtedly  due  to  the  flattening 
of  the  cornea  corresponding  to  the  section,  making  one 


Fig.  51. 

portion  myopic  and  the  other  hyperopic.  Figure  51 
with  correcting  sphere  in  position,  shows  such  a  condition, 
where  the  upper  illumination  would  move  with  and  the 
lower,  being  myopic,  would  move  against  the  movement  of 
the  mirror. 

Compound  Irregular  Astigmatism. — This  is  a  com- 
bination of  the  scissor  movement  and  regular  astigmatism, 
but  they  are  not  at  right  angles  to  each  other.  The  scissor 
movement  may  be  at  180°,  and  the  regular  astigmatism 
at  some  point  away  from  90°,  but  not  at  90°;  or  the  regular 
astigmatism  may  be  at  90°  and  the  scissor  movement  at 
some  meridian  other  than  180°. 

A  hasty  review  of  the  literature  of  astigmatism  does  not 
reveal  any  reference  to  this  form,  and  the  name  for  the 
condition  has  been  suggested  by  the  following  picture, 


6o  RETINOSCOPY. 

namely:  When  studying  the  reflex,  a  vertical  band  of 
light  will  be  seen  passing  across  the  pupillary  area  from 
left  to  right  as  the  mirror  is  turned,  and  then  in  the  vertical 
meridian  {not  at  right  angles)  the  scissor  movement  will 
be  recognized  also;  there  is,  therefore,  a  combination  of 
regular  •  corneal  astigmatism  with  the  scissor  movement 
at  an  oblique  angle,  giving  the  compound  name  suggested. 
This  form  of  astigmatism  is  rare,  yet  not  difficult  to  diagnose 
or  refract  when  understood.  It  is  hoped,  however,  that  the 
beginner  in  retinoscopy  may  not  meet  one  of  these  on  his 
first  attempt  at  the  human  eye.     (See  page  67.) 

Conic  Cornea.— Reflecting  the  light  into  an  eye  that 
has  such  a  condition,  the  observer  is  impressed  at  once 


Fig.  52. — Illumination  Seen  in  Conic  Cornea. 

with  the  bright  central  illumination  that  moves  opposite 
to  the  movement  of  the  mirror,  the  peripheral  illumination 
moving  with,  unless  perchance  the  margin  should  be 
myopic  also,  but  of  less  degree.  This  form  of  illumina- 
tion is  seen  in  Figure  52,  showing  the  central  illumination 
faintly  separated  by  a  shaded  area  or  ring  from  the  per- 
ipheral circle.  The  best  way  to  refract  a  case  of  this  kind  is 
to  keep  a  record  of  the  neutralizing  lens  or  lenses  required 
for  the  portion  of  the  pupillary  area  that  will  correspond 
to  the  size  of  the  pupil  after  the  effect  of  the  cycloplegic 
passes  away,  and  use  this  record  as  a  guide  in  a  post-cyclo- 
plegic  manifest  correction,  as  in  irregular  corneal  astig- 
matism. 

As  the  apex  of  the  cone  is  not  always  central,  the  observer 
must  not  expect  to  always  find  the  bright  illumination  in 


SPHERIC  ABERRATION.  6 1 

the  center  of  the  pupillary  area,  as  just  mentioned;  and  it  is 
also  well  to  note  the  fact  that  a  band  of  light  will  often 
appear  during  the  process  of  neutralization,  as  astigmatism 
is  usually  present.     This  is  further  described  on  page  66. 

Spheric  Aberration. — This  appears  under  two  forms, 
positive  or  negative,  and  is  the  condition  in  which,  during 
the  process  of  neutralization,  there  are  two  zones,  one 
central  and  the  other  peripheral,  where  the  refraction  is 
not  the  same.  In  positive  aberration  the  peripheral  refrac- 
tion is  stronger  and  in  negative  abberation  the  peripheral 


Fig.  53. — Positive  Aberration, 

is  weaker  than  the  central  area;  that  is  to  say,  in  the  positive 
form,  when  the  point  of  reversal  for  the  center  of  the  pupil 
is  close  to  one  meter,  the  peripheral  illumination  grows 
broader  and  has  a  tendency  to,  and  often  will,  crowd  in 
upon  the  small  central  illumination,  giving  the  idea  of 
neutralization,  or  even  the  appearance  of  over-correction, 
the  illumination  in  the  periphery  moving  opposite.  The  ob- 
server must  be  on  his  guard  for  this  condition,  and  while 
giving  the  mirror  a  slow  and  limited  rotation  must  watch 
carefully  the  illumination  in  the  center  of  the  pupil  and 
not  hasten  the  peripheral  movement.  (See  What  to  Avoid, 
p.  30,  Chap.  IV.)  The  observer  may  have  to  approach 
the  patient's  eye  closer  than  one  meter  if  the  peripheral 
illumination  appears  to  move  very  fast.  The  negative 
form  is  where  the  peripheral  refraction  is  weak  as  com- 
pared to  the  central  which  appears  strong,  and  when  the 
neutralizing  lens  gives  a  point  of  reversal  to  the  center  of 


62 


RETINOSCOPY. 


the  pupil  the  peripheral  illumination  still  moves  with  the 
movement  of  the  mirror.  This  condition  is  seen  in  cases 
of  conic  cornea. 

Figure  53  illustrates  positive  abberration  where  the  paral- 
lel rays  passing  through  a  convex  lens  in  the  periphery  at 
A  A  come  to  a  focus  at  ^',  much  sooner  than  the  parallel 
rays  B  B,  near  the  center,  which  comes  to  a  focus  back 
of  A'  Sit  B'. 

Figure  $4  illustrates  negative  abberation,  which  is  the 
reverse  of  positive  aberration,  and  the  central  rays  B  B 
are  focused  at  B'  in  front  of  the  peripheral  rays  A  A  focus- 
ing at  ^'. 


Fig.  54. — Negative  Aberrationt. 

Retinoscopy  Without  a  Cycloplegic. — Cases  of  my- 
opia and  mixed  astigmatism  which  have  large  pupils  can  be 
quickly  and  accurately  refracted  by  the  shadow  test  without 
the  use  of  a  cycloplegic.  This  has  been  repeatedly  proven 
by  comparison  of  the  manifest  and  cycloplegic  results; 
yet  it  is  not  a  method  to  be  recommended  or  pursued,  for 
two  reasons:  One  is  that  these  patients  are  not  annoyed, 
like  hyperopics,  by  the  blurred  near-vision  incident  to  the 
cycloplegic;  and,  secondly,  glasses  ordered  without  the 
cycloplegic  seldom  give  the  comfort  that  follows  from  the 
physiologic  rest  the  eye  receives  from  the  drug.  The 
surgeon  will  obtain  much  assistance  and  save  time  by  using 
the  retinoscope  in  cases  of  aphakia,  in  old  persons  especially 
who  are  very  slow  to  answer,  and  will  insist  upon  a  descrip- 
tion of  what  they  do  and  do  not  see,  as  also  in  re-reading 


SCHEMATIC    EYE    FOR    STUDYING    RETINOSCOPY.  6 


the  test-card  from  the  very  top  each  time  a  change  of  lens 
is  put  in  the  trial-frame.  Presbyopes  of  fifty  or  more  years 
of  age  can  be  quickly  and  not  inconveniently  refracted  by 
the  shadow  test  after  having  their  pupils  dilated  with  a 
weak  (four  per  cent.)  solution  of  cocain. 

Concave  Mirror. — While  the  study  of  retinoscopy  with 
the  concave  mirror  is  not  a  part  of  the  subject  of  this 
book,  and  allusion  to  it  has  been  carefully  avoided  up  to 
this  time,  yet  for  the  benefit  of  those  who  may  wish  to  try  it, 
the  writer  would  suggest  that  it  will  be  necessary  to  place 
the  source  of  light  (20  or  30  mm.  opening  in  light-screen) 
above  and  beyond  the  patient's  head,  one  meter  distant, 
or  more,  so  that  the  convergent  rays  from  the  mirror  come 
to  a  focus  and  cross  before  entering  the  observed  eye. 
Then  to  estimate  the  refraction,  proceed  as  with  the  plane 
mirror,  remembering,  however,  that  the  movements  of  the 
retinal  illumination  are  just  the  reverse  of  those  obtained 
when  using  the  plane  mirror. 

The  Author's  Schematic  Eye  for  Studying  Retin- 
oscopy.— ^For  illustration  see  Figure  i .  and  the  Journal 
of  the  American  Medical  Association,  January  5,  1895. 
The  eye  is  here  shown,  slightly  reduced  in  size,  is  made  of 
two  brass  cylinders,  one  somewhat  smaller  than  its  fellow, 
to  permit  slipping  evenly  into  the  other.  Both  cylinders 
are  well  blackened  outside.  The  smaller  cylinder  is  closed 
at  one  end  (concave  surface),  and  on  its  inner  surface  is 
placed  a  colored  lithograph  of  the  normal  eye  ground. 
The  larger  cylinder  is  also  closed  at  one  end,  except  for  a 
central  round  opening  10  mm.  in  diameter,  which  is  occupied 
by  a  4- 16  D.  lens,  and  on  its  outer  surface  is  a  colored 
lithograph  of  the  normal  eye  and  its  appendages;  the  pupil 
is  left  dilated,  and  corresponds  in  size  to  the  central  opening 
just  referred  to.  In  addition  to  the  picture  of  the  eye, 
there  is  also  lithographed  on  the  upper  half  of  the  periphery 


64  RETINOSCOPY. 

the  degree  marks  similar  to  those  on  a  trial-frame.  To 
the  lower  half  of  the  periphery  are  secured,  at  equal  dis- 
tances, three  posts  with  grooves  to  hold  trial-lenses.  On 
the  side  of  the  small  cylinder  is  an  index  which  records 
emmetropia,  and  the  amount  of  myopia  and  hyperopia,  as 
it  is  pushed  into  or  drawn  out  of  the  large  cylinder.  The 
eye  is  mounted  on  a  convenient  stand  and  upright,  so  that 
it  may  be  moved  as  required.  In  using  this  eye,  if  the  red 
eye  ground  and  retinal  vessels  disturb  the  beginner,  then 
he  may  substitute  a  piece  of  white  paper  for  the  retina. 
To  study  astigmatism  with  the  model,  the  beginner  will 
have  to  place  a  cylinder  of  known  strength  in  the  groove 
next  to  the  eye  and  study  the  characteristic  band  of  light 
so  diagnostic  of  this  condition,  and  at  the  same  time  he 
should  learn  to  locate  the  axis  of  the  band  with  the  axo- 
nometer. 

The  author's  light-screen  or  cover  chimney  (see 
Figure  7  and  the  Annals  of  Ophthalmology  and  Otology, 
October,  1896)  is  made  of  one-eighth  inch  asbestos,  and  of 
sufficient  size  to  fit  easily  over  the  glass  chimney  of  the 
Argand  burner;  attached  to  the  asbestos  by  means  of  a 
metal  clamp  are  two  superimposed  discs,  which  revolve 
independently  of  each  other.  The  lower  disc  contains  a 
piece  of  white  procelain,  30  mm.  in  diameter;  also  four 
round  openings,  respectively  5,  10,  20,  and  35  mm.  in 
diameter.  The  upper  disc  contains  a  round  35  mm. 
opening,  a  round  section  of  blue  cobalt  glass,  a  perforated 
disc,  a  vertical  and  a  horizontal  slit,  each  2  1/2  by  25  mm. 
The  several  uses  of  this  screen  are  as  follows : 

I-.  For  the  ophthalmoscope  a  good  light  is  obtained  by 
superimposing  the  two  35  mm.  openings. 

2.  Combining  the  35  mm.  opening  in  the  upper  with 
either  the  5  or  10  mm.  in  the  lower  disc,  a  source  of  light 
is  produced  for  the  small  retinoscope;  and. 


SCISSOR    MOVEMENT,    CONIC    CORNEA,   ABERRATION.     65 

3.  By  substituting  the  20  mm.  opening,  light  is  had  for 
the  concave  mirror. 

4.  Placing  the  cobalt  glass  over  the  5,  10,  20,  or  35  mm. 
opening,  and  the  chromo-aberration  test  for  ametropia  is 
given. 

5.  To  test  for  astigmatism,  at  one  meter  while  using  the 
plane  mirror,  or  for  heterophoria  at  six  meters,  the  per- 
forated disc  is  to  be  turned  over  the  porcelain,  the  latter 
producing  a  clear  white  image. 

6.  The  horizontal  slit  placed  over  the  porcelain  glass, 
and  the  operator  may  exercise  the  oblique  muscles. 

7.  The  vertical  slit  similarly  placed  gives  the  test  for 
paralyzed  muscles. 

Lenses  for  the  Study  of  the  Scissor  Movement, 
Conic  Cornea,  Spheric  Aberration,  and  Lenticular 
Astigmatism. — (Described  by  the  author  in  the  Journal 
of  the  American  Medical  Association,  December  18,  1897.) 

As  the  scissor  movement,  conic  cornea,  spheric  aberration, 
and  lenticular  astigmatism,  as  recognized  by  the  retino- 
scope,  are  so  difficult  of  demonstration,  except  in  the 
individual  patient,  the  writer  has  suggested  and  had  made 
four  lenses  which  will  illustrate  these  conditions  respectively 
when  placed  in  front  of  his  schematic  eye;  and  thus  the 
beginner  in  retinoscopy  may  have  the  opportunity  to  see, 
know,  and  study  these  important  and  interesting  manifes- 
tations (and  at  small  expense)  before  prodceeding  direct 
and  in  comparative  ignorance  to  his  patient. 

Figures  55  and  56  represent  a  plano-concave  cylinder 
of  two  diopters,  mounted  in  a  cell  of  the  trial-case,  and  to 
one-half  of  its  plane  surface  is  cemented  (at  the  same  axis) 
a  plano-convex  cylinder  of  four  diopters,  thus  making  a 
combination  lens,  one-half  of  which  is  a— 2  D.  and  the 
other  half  equaling  a  +  2  D.  Placing  this  lens,  with  its 
axis  at  180°,  before  the  schematic  eye  at  emmetropia  (zero), 
S 


66 


RETINOSCOPY. 


and  the  observer  at  one  meter  distance  with  his  plane 
mirror,  the  two  light  areas  characteristic  of  the  scissor 
movement,  with  their  comparatively  straight  edges  and 
dark  interspace  may  be  seen  approaching  each  other 
from  above  and  below  (and  the  dark  interspace  disappear- 
ing) as  the  mirror  is  tilted  in  the  vertical  meridian. 

Figures  57  and  58  represent  a  section  of  thin  plane  glass 
mounted  as  in  Figure  55  and  has  cemented  at  its  center 
a  small  plano-convex  sphere  of  three  diopters,  whose  base 


+aoi 


-ao) 


Fig.  55.  Fig.  57.  Fig.  59.  . 


is  about  four  mm.  in  diameter.  Placing  this  lens  in  front 
of  the  schematic  eye  at  emmetropia,  and  reflecting  the 
light  from  the  plane  mirror  at  one  meter,  there  will  be  seen 
in  the  pupillary  area  a  small  central  illumination,  which 
moves  against  or  opposite  to  the  movement  of  the  mirror, 
and  at  the  same  time  there  will  also  be  seen  a  peripheral 
ring  (at  the  edge  of  the  iris)  which  moves^  rapidly  with 
the  movement  of  the  mirror;  between  these  light  areas  is 
a  shaded  ring  of  feeble  illumination.  This  is  the  retino- 
scopic  picture  and  movement  of  the  light  areas,  so  indica- 
tive of  conic  cornea.  It  is  also  an  exaggerated  picture  of 
negative  aberration. 

Figures  59  and  60  represent  a  section  similar  to  that 
shown  in  Figures  57  and  58,  except  that  at  its  center  is 


SCISSOR   MOVEMENT,    CONIC   CORNEA,   ABERRATION.     67 

ground  a  —  2  D.  sphere  of  about  four  mm.  in  diameter. 
To  produce  spheric  aberration  of  the  positive  form,  place 
this  lens  in  front  of  the  schematic  eye  at  emmetropia,  and 
the  observer,  seated  at  one  meter  distance  with  the  plane 
mirror,  will  see  in  the  pupillary  area  a  central  illumination 
which  moves  slower  than  the  peripheral  area  or  ring  (at 
the  edge  of  the  iris),  which  moves  rapidly,  both  areas 
moving  with  the  movement  of  the  mirror.  Figure  61 
shows  a  lens  for  studying  lenticular  astigmatism.  This 
is  made  by  scratching  a  piece  of  plane  glass  with  a  diamond. 


Fig.  56.  Fig.  58. 

After  the  observer  has  carefully  studied  these  pictures 
it  will  be  obvious  that  changes  other  than  those  mentioned 
can  be  made  with  these  lenses,  and  he  should  proceed 
to  note  them  by — 

1.  Changing  the  focus  of  the  schematic  eye. 

2.  By  varying  his  distance  from  the  eye. 

3.  By  placing  both  the  concave  and  convex  spheres  in 
combination. 

4.  By  placing  a  concave  cylinder  in  front  of  the  double 
cylinder  at  an  oblique  axis,  thus  getting  a  picture  of 
compound   irregular  astigmatism. 

5.  By  placing  a  concave  cylinder  in  front  of  the  convex 
sphere  and  developing  astigmatism  with  the  conic  cornea, 


68 


RETINOSCOPY. 


which  is  the  usual  condition;  or  a  convex  cylinder  might 
be  used  in  place  of  the  concave  cylinder  if  a  higher  error 
is  desired. 

6.  It  is  obvious,  also,  that  the  scissor  movement  can  be 


Fig.  6o. 


Fig.  6i. 


produced  by  a  prism  which  is  made  to  cover  one-half  of  the 
pupillary  area,  but  the  resulting  picture  is  not  so  satis- 
factory for  demonstration  as  that  given  by  the  combination 
lens  referred  to  in  Figure  55. 


NDEX. 


Aberration,  negative,  6i 

positive,  6 1 

spheric,  6i 
Accommodation,  15,  1 6 
Accuracy,  2,  28,  29 

advantages  of,  2,  3 
Albino,  23 
Amblyopia,  3,  4 
Aphakia,  3 

Apparatus,  3,  33,  34,  35,  36 
Area  of  light,  24 
Argand  burner,  9,  10 
Arrangement  of  light,  18,  19 

of  observer,  18,  19 

of  patient,  18,  19 
Astigmatism,  32,  44,  46 

compound  irregular,  59 

corneal,  44 

irregular,  54 

lenticular,  55 

regular,  44 
Author's  axonometer,  35 

retinoscope,  6,  7,  8,  12,  13,  14 

schematic  eye,  3,  4,  (Chap.  VI), 
22,  63 

schematic  lenses,  65 

shade,  9,  10,  12,  13,  64,  65 

trial-case,  36 

trial-frame,  35 

trial-lenses,  65 
Avoid,  what  to,  30,  31 
Axiom,  2 
Axonometer,  celluloid,  16,  50 

metal,  47,  50 

Band  of  light,  45,  46,  47 

Bands  of  Ught,  55,  56,  57,  58,  59 

causes  of,  58 
Beginner,  4,  5 
Bracket,  extension,  9 
Brunette,  23 
Burner,  Argand,  9,  10 

Catoptric  images,  24,  30 


Central  shadow,  30 

illumination,  25,  30 
Children,  3 
Cocain,  62 

Compound  irregular  astigmatism,  59 
Concave  mirror,  63 
Conic  cornea,  60 

astigmatism  in,  60,  61 
Conjugate  focus,  4,  27 
Cornea,  apex,  25,  60 
Cover  chimney,  9,  10,  12,  13 
Correct  position,  2 1 
Crossed  cylinders,  47,  48 
Cycloplegic,  2,  4,  15,  62 

Darkness,  24,  25 

Dark  room,  11,  12 

Definition,  i  (Preface) 

De  Zeng,  13,  14,  15 

Dioptroscopy,  i 

Direction  of  movement,  25,  28,  31 

Disc,  30,  31 

Distance,  17,  18,  19,  28 

Emmetropia,  28,  39,  40 
Examples,  27,  28,  38,  41,  44,  45 

Facial  illumination,  28 

Fantoscopy,  i 

Far-point,  i,  27 

Feeble-minded,  3 

Fixation  letters,  15 

Flame,  7,  8,  9 

Form  of  illumination,  25,  31,  32 

Formula,  27,  28 

Fundus-reflex,  test,  i 

General  appearances,  22,  23 

How  to  use  the  mirror,  20,  2 1 
Hyaloid  vessel,  30 
Hyperopia,   28,  31,  37,  38,' 
Hyperopic  astigmatism,  44 


69 


70 


INDEX. 


Illiterates,  3 

Illuminated  area,  24,  25 
Illumination,  facial,  28 

form  of,  25,  32 

retinal,  24,  25 
Image,  24,  25 
Images,  24,  25,  27,  30 
Inaccuracy,  4 
Irregular  astigmatism,  54 

Jackson  (Preface),  6 
Jennings,  34 

Kaleidoscope,  54 
Keratoscopy,  i 
Koroscopy,  i 

Lamp,  electric,  8,  9 

gas,  9 

oil,   9 
Lenses,  neturalizing,  4,  18,  23,  30,  32 

rule  for,  30,  32 

schematic,  65 
Lenticular  astigmatism,  55 
Lettered  retinoscope,  8 
Light,  8,  9,  II,  12 

electric,  8,  9,  13,  14 

gas,  9 

oil,  9 

Welsbach,  8 
Light-screen,  9,  10,  11,  12,  13 
Luminous  retinoscope,  14,  15 

Macula,  16 
Macular  region,  16 
Magnification,  point  of,  27 
Meter  distance,  17,  18,  19 

stick,  17 
Mirror,  6,  7,  8,  9,  20,  21,  22,  63 
Mixed  astigmatism,  47,  48 
Movement  of  light,  20,  32 

in  pupillary  area,  22,  27,  30 

on  face,  27 

of  mirror,  20,  25,  32,  33 
Mulatto,  23 
Myopia,  17,  27,  28,  31,  40,  41 

Name,  i 

Negative  aberration,  62 

Neutralizing  lenses,  4,  18,  23,  30,  32 

rules  for,  30,  32 
Nystagmus,  3 

Observer,  12,  13,  17,  19 
Oculist,  19 


Oil-lamp,  9 
Ophthalmoscope,  2,  12 

Patient,  15,  16,  17 

Pearse,  Dr.,  49 

Point  of  magnification,  27 

of  reversal,  i,  (Chap.  IV),  13, 
14,  17,  18,  27,  29 
Position  of  light,  12,  13 

of  mirror,  12,  13 

of  observer,  12,  13 

of  patient,  12 

of  lenses,  4,  18,  23,  30,  32 
Positive  aberration,  61 
Post-cycloplegic,  60 
Principle  of  retinoscopy,  i,  27 
Punctum  remotum,  i,  27 
Pupillary  area,  22,  25 
Pupilloscopy,  I 

Quick  movement,  20,  32,  33 

Rate  of  movement  of  illumination, 
20,  25,  32 

of  mirror,  20,  32 
Reflection  from  cornea,  24,  30 

from  lenses,  24,  30 

from  mirror,  19,  20 
Refraction  at  center  of  pupil,  29,  30, 

at  pupillary  edge,  25 
Regular  astigmatism,  44,  45 
Retinal  illumination,  24,  25,  29,  30, 

31 

image,  24 

vessel,  30 
Retinophotoscopy,  i 
Retinoscope,  6,  7,  8,  12,  13,  14 
Retinoscopy,  i 

advantages,  2,  3 

in  amblyopia,  3,  4 

in  children,  3,  4 

in  feeble-minded,  3 

in  nystagmus,  3 

without  a  cycloplegic,  62 
Retinoskiascopy,  i 
Reversal  of  movement,  30 
Room,  II,  12 
Rule,  Pearse's,  49 
Rules  for  distance,  17,  18,  19,  28 

for  lenses,  32,  43,  44 

Schematic  eye,  3,  4,  (Chap.  VI)  22, 

lenses,  65,  66,  67 
Scissor  movement,  55,  56,  57 
Shade,  9,  10,  12,  13 


INDEX. 


71 


Shadow,  24,  25 

test,  I,  25 
Sight-hole,  6,  30 
Size  of  mirror,  6 

of  sight-hole,  6 
Skiagraphy,  i 
Skiascopy,  i 

Slow  movement,  20,  32,  ^^ 
Source  of  light,  11,  12 
Spheric  aberration,  61 
Squint,  16 

use  of  axonometer,  in  cases  of,  61 
Suggestions  to  the  beginner,  4,  5 
Surgeon,  17 

Thorington,  3,  6,  9,  35,  36,  65 


Trial-case,  36 

-frame,  35 
Tungston  lamp,  15 

Umbrascopy,  i 

Value  of  retinoscopy,  2 
Vision  of  observer,  12 

Welsbach,  8 

What  the  observer  sees,  22,  23 

to  avoid,  30,  31 
Where  to  look,  and  what  to  look  for, 

25,  26 
Wiirdemann,  33,  34 

Young  children,  3 


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